diff --git a/src/gadget/sha256/table16/compression.rs b/src/gadget/sha256/table16/compression.rs
index 3b1c4d3a..7bb8bde2 100644
--- a/src/gadget/sha256/table16/compression.rs
+++ b/src/gadget/sha256/table16/compression.rs
@@ -12,7 +12,7 @@ use crate::{
 mod compression_gates;
 mod compression_util;
 // mod subregion_digest;
-// mod subregion_initial;
+mod subregion_initial;
 // mod subregion_main;
 
 use compression_gates::CompressionGate;
@@ -681,7 +681,14 @@ impl Compression {
         init_state: [u32; STATE],
     ) -> Result<State, Error> {
         let mut new_state = State::empty_state();
-        todo!()
+        layouter.assign_region(
+            || "initialize_with_iv",
+            |mut region| {
+                new_state = self.initialize_iv(&mut region, init_state)?;
+                Ok(())
+            },
+        )?;
+        Ok(new_state)
     }
 
     /// Initialize compression with some initialized state. This could be a state
@@ -692,7 +699,14 @@ impl Compression {
         init_state: State,
     ) -> Result<State, Error> {
         let mut new_state = State::empty_state();
-        todo!()
+        layouter.assign_region(
+            || "initialize_with_state",
+            |mut region| {
+                new_state = self.initialize_state(&mut region, init_state.clone())?;
+                Ok(())
+            },
+        )?;
+        Ok(new_state)
     }
 
     /// Given an initialized state and a message schedule, perform 64 compression rounds.
diff --git a/src/gadget/sha256/table16/compression/subregion_initial.rs b/src/gadget/sha256/table16/compression/subregion_initial.rs
new file mode 100644
index 00000000..ca5a78bd
--- /dev/null
+++ b/src/gadget/sha256/table16/compression/subregion_initial.rs
@@ -0,0 +1,156 @@
+use super::super::{RoundWordDense, RoundWordSpread, StateWord, Table16Chip, STATE};
+use super::{compression_util::*, Compression, State};
+use crate::{arithmetic::FieldExt, circuit::Region, plonk::Error};
+
+impl Compression {
+    pub fn initialize_iv<F: FieldExt>(
+        &self,
+        region: &mut Region<'_, Table16Chip<F>>,
+        iv: [u32; STATE],
+    ) -> Result<State, Error> {
+        let a_7 = self.extras[3];
+
+        let idx = -1;
+
+        // Decompose E into (6, 5, 14, 7)-bit chunks
+        let e = self.decompose_e(region, idx, iv[4])?;
+
+        // Decompose F, G
+        let f = self.decompose_f(region, idx, iv[5])?;
+        let g = self.decompose_g(region, idx, iv[6])?;
+
+        // Assign H
+        let h_row = get_h_row(idx);
+        let h_dense = self.assign_word_halves_dense(region, h_row, a_7, h_row + 1, a_7, iv[7])?;
+        let h = RoundWordDense::new(h_dense);
+
+        // Decompose A into (2, 11, 9, 10)-bit chunks
+        let a = self.decompose_a(region, idx, iv[0])?;
+
+        // Decompose B, C
+        let b = self.decompose_b(region, idx, iv[1])?;
+        let c = self.decompose_c(region, idx, iv[2])?;
+
+        // Assign D
+        let d_row = get_d_row(idx);
+        let d_dense = self.assign_word_halves_dense(region, d_row, a_7, d_row + 1, a_7, iv[3])?;
+        let d = RoundWordDense::new(d_dense);
+
+        Ok(State::new(
+            StateWord::A(a),
+            StateWord::B(b),
+            StateWord::C(c),
+            StateWord::D(d),
+            StateWord::E(e),
+            StateWord::F(f),
+            StateWord::G(g),
+            StateWord::H(h),
+        ))
+    }
+
+    pub fn initialize_state<F: FieldExt>(
+        &self,
+        region: &mut Region<'_, Table16Chip<F>>,
+        state: State,
+    ) -> Result<State, Error> {
+        let a_7 = self.extras[3];
+        let (a, b, c, d, e, f, g, h) = match_state(state);
+
+        let idx = -1;
+
+        // Decompose E into (6, 5, 14, 7)-bit chunks
+        let e = val_from_dense_halves(e.dense_halves);
+        let e = self.decompose_e(region, idx, e)?;
+
+        // Decompose F, G
+        let f = val_from_dense_halves(f.dense_halves);
+        let f = self.decompose_f(region, idx, f)?;
+        let g = val_from_dense_halves(g.dense_halves);
+        let g = self.decompose_g(region, idx, g)?;
+
+        // Assign H
+        let h = val_from_dense_halves(h.dense_halves);
+        let h_row = get_h_row(idx);
+        let h_dense = self.assign_word_halves_dense(region, h_row, a_7, h_row + 1, a_7, h)?;
+        let h = RoundWordDense::new(h_dense);
+
+        // Decompose A into (2, 11, 9, 10)-bit chunks
+        let a = val_from_dense_halves(a.dense_halves);
+        let a = self.decompose_a(region, idx, a)?;
+
+        // Decompose B, C
+        let b = val_from_dense_halves(b.dense_halves);
+        let b = self.decompose_b(region, idx, b)?;
+        let c = val_from_dense_halves(c.dense_halves);
+        let c = self.decompose_c(region, idx, c)?;
+
+        // Assign D
+        let d = val_from_dense_halves(d.dense_halves);
+        let d_row = get_d_row(idx);
+        let d_dense = self.assign_word_halves_dense(region, d_row, a_7, d_row + 1, a_7, d)?;
+        let d = RoundWordDense::new(d_dense);
+
+        Ok(State::new(
+            StateWord::A(a),
+            StateWord::B(b),
+            StateWord::C(c),
+            StateWord::D(d),
+            StateWord::E(e),
+            StateWord::F(f),
+            StateWord::G(g),
+            StateWord::H(h),
+        ))
+    }
+
+    fn decompose_b<F: FieldExt>(
+        &self,
+        region: &mut Region<'_, Table16Chip<F>>,
+        idx: i32,
+        b_val: u32,
+    ) -> Result<RoundWordSpread, Error> {
+        let row = get_decompose_b_row(idx);
+
+        let (dense_halves, spread_halves) = self.assign_word_halves(region, row, b_val)?;
+        self.decompose_abcd(region, row, b_val)?;
+        Ok(RoundWordSpread::new(dense_halves, spread_halves))
+    }
+
+    fn decompose_c<F: FieldExt>(
+        &self,
+        region: &mut Region<'_, Table16Chip<F>>,
+        idx: i32,
+        c_val: u32,
+    ) -> Result<RoundWordSpread, Error> {
+        let row = get_decompose_c_row(idx);
+
+        let (dense_halves, spread_halves) = self.assign_word_halves(region, row, c_val)?;
+        self.decompose_abcd(region, row, c_val)?;
+        Ok(RoundWordSpread::new(dense_halves, spread_halves))
+    }
+
+    fn decompose_f<F: FieldExt>(
+        &self,
+        region: &mut Region<'_, Table16Chip<F>>,
+        idx: i32,
+        f_val: u32,
+    ) -> Result<RoundWordSpread, Error> {
+        let row = get_decompose_f_row(idx);
+
+        let (dense_halves, spread_halves) = self.assign_word_halves(region, row, f_val)?;
+        self.decompose_efgh(region, row, f_val)?;
+        Ok(RoundWordSpread::new(dense_halves, spread_halves))
+    }
+
+    fn decompose_g<F: FieldExt>(
+        &self,
+        region: &mut Region<'_, Table16Chip<F>>,
+        idx: i32,
+        g_val: u32,
+    ) -> Result<RoundWordSpread, Error> {
+        let row = get_decompose_g_row(idx);
+
+        let (dense_halves, spread_halves) = self.assign_word_halves(region, row, g_val)?;
+        self.decompose_efgh(region, row, g_val)?;
+        Ok(RoundWordSpread::new(dense_halves, spread_halves))
+    }
+}