diff --git a/crates/dwg/src/lib.rs b/crates/dwg/src/lib.rs
index 9fe25dc3..7c7da02a 100644
--- a/crates/dwg/src/lib.rs
+++ b/crates/dwg/src/lib.rs
@@ -330,7 +330,8 @@ mod native {
     /// the HEADER section: (name, group code, value).
     fn unwritten_header_vars(h: &acadrust::document::HeaderVariables) -> [(&'static str, i32, String); 7] {
         [
-            ("$ANGBASE", 50, h.angle_base.to_string()),
+            // DWG holds radians; `$ANGBASE` is in degrees.
+            ("$ANGBASE", 50, h.angle_base.to_degrees().to_string()),
             ("$ANGDIR", 70, h.angle_direction.to_string()),
             ("$FILLETRAD", 40, h.fillet_radius.to_string()),
             ("$CHAMFERA", 40, h.chamfer_distance_a.to_string()),
diff --git a/crates/engine/src/sysvars.rs b/crates/engine/src/sysvars.rs
index 0dd7503b..6cb6b9e9 100644
--- a/crates/engine/src/sysvars.rs
+++ b/crates/engine/src/sysvars.rs
@@ -130,7 +130,7 @@ pub fn get(s: &Session, name: &str) -> Option<Value> {
         "MAXARRAY" => json!(st.maxarray),
         "ZOOMFACTOR" => json!(st.zoomfactor),
         "LASTPOINT" => json!([s.last_point.x, s.last_point.y, 0.0]),
-        // Held in radians (as `$ANGBASE` in DXF); reported in degrees, like POLARANG.
+        // Held in radians (`$ANGBASE` in DXF is in degrees); reported in degrees, like POLARANG.
         "ANGBASE" => json!(s.doc().ok()?.header.f64("ANGBASE", 0.0).to_degrees()),
         "CONSTRAINTINFER" => json!(i32::from(s.doc().ok()?.parametric.settings.infer)),
         // Process-wide font substitution (profile settings, not saved in the drawing).
diff --git a/crates/engine/src/units.rs b/crates/engine/src/units.rs
index dd15111c..44af14f9 100644
--- a/crates/engine/src/units.rs
+++ b/crates/engine/src/units.rs
@@ -157,7 +157,7 @@ fn parse_mixed(s: &str) -> Option<f64> {
 pub struct AngleSettings {
     /// AUNITS: 0 decimal degrees, 1 degrees/minutes/seconds, 2 grads, 3 radians, 4 surveyor's.
     pub aunits: i64,
-    /// ANGBASE: the direction of angle 0, in radians counterclockwise from +X (as `$ANGBASE` in DXF).
+    /// ANGBASE: the direction of angle 0, in radians counterclockwise from +X (`$ANGBASE` in DXF is in degrees).
     pub angbase: f64,
     /// ANGDIR 1: positive angles turn clockwise.
     pub clockwise: bool,
diff --git a/crates/io/src/dxf_read.rs b/crates/io/src/dxf_read.rs
index c043842e..92d803e1 100644
--- a/crates/io/src/dxf_read.rs
+++ b/crates/io/src/dxf_read.rs
@@ -1341,6 +1341,9 @@ fn header(tags: &[Tag], d: &mut Drawing) {
                 },
                 // $DIMJOGANG is in radians; the variable (like the style) holds degrees.
                 HVal::Real(r) if name == "DIMJOGANG" => HVal::Real((r.to_degrees() * 1e9).round() / 1e9),
+                // $ANGBASE is in degrees (a drawing measured from north has 90.0); the variable
+                // holds radians.
+                HVal::Real(r) if name == "ANGBASE" => HVal::Real(r.to_radians()),
                 hv => hv,
             };
             d.header.set(&name, hv);
diff --git a/crates/io/src/dxf_write.rs b/crates/io/src/dxf_write.rs
index 3fdf3258..521654e3 100644
--- a/crates/io/src/dxf_write.rs
+++ b/crates/io/src/dxf_write.rs
@@ -358,6 +358,8 @@ fn header_vars(w: &mut W, d: &Drawing) {
             (-2 | -3, _) => {}
             (c @ (40 | 50), v) => {
                 if let Some(f) = v.as_f64() {
+                    // ANGBASE is held in radians; `$ANGBASE` is in degrees.
+                    let f = if *name == "ANGBASE" { f.to_degrees() } else { f };
                     w.s(9, format!("${name}"));
                     w.f(c, f);
                 }
diff --git a/crates/io/tests/angle_header.rs b/crates/io/tests/angle_header.rs
index 1b39f820..e9b29da3 100644
--- a/crates/io/tests/angle_header.rs
+++ b/crates/io/tests/angle_header.rs
@@ -1,5 +1,6 @@
-//! The angle settings round-trip through DXF: `$ANGBASE` (group 50) in radians, `$ANGDIR` and
-//! `$AUNITS` (group 70) as integers.
+//! The angle settings round-trip through DXF: `$ANGBASE` (group 50) in degrees, as AutoCAD writes
+//! it (a drawing measured from north has 90.0), held in radians; `$ANGDIR` and `$AUNITS`
+//! (group 70) as integers.
 
 use cadcraft_doc::{Drawing, HVal};
 
@@ -10,9 +11,23 @@ fn angbase_angdir_aunits_round_trip_through_dxf() {
     d.header.set_i64("ANGDIR", 1);
     d.header.set_i64("AUNITS", 3);
     let text = cadcraft_io::write_dxf(&d);
+    // Written in degrees.
+    let lines: Vec<&str> = text.lines().map(str::trim).collect();
+    let at = lines.iter().position(|l| *l == "$ANGBASE").expect("$ANGBASE is written");
+    let written: f64 = lines.get(at + 2).and_then(|v| v.parse().ok()).expect("a number");
+    assert!((written - 90.0).abs() < 1e-9, "$ANGBASE written as {written}");
     let r = cadcraft_io::read_dxf(text.as_bytes()).unwrap();
     let base = r.header.f64("ANGBASE", 0.0);
     assert!((base - std::f64::consts::FRAC_PI_2).abs() < 1e-12, "$ANGBASE read back as {base}");
     assert_eq!(r.header.get("ANGDIR"), Some(&HVal::Int(1)));
     assert_eq!(r.header.get("AUNITS"), Some(&HVal::Int(3)));
 }
+
+#[test]
+fn angbase_in_degrees_is_read_as_radians() {
+    // What AutoCAD writes for a drawing whose angles run clockwise from north.
+    let text = "0\nSECTION\n2\nHEADER\n9\n$ANGBASE\n50\n90.0\n9\n$ANGDIR\n70\n1\n0\nENDSEC\n0\nEOF\n";
+    let d = cadcraft_io::read_dxf(text.as_bytes()).unwrap();
+    let base = d.header.f64("ANGBASE", 0.0);
+    assert!((base - std::f64::consts::FRAC_PI_2).abs() < 1e-12, "$ANGBASE 90.0 read as {base} radians");
+}