diff --git a/spec.md b/spec.md
index 64ecd1c..cf2c1e0 100644
--- a/spec.md
+++ b/spec.md
@@ -239,3 +239,14 @@
 | StoreAccessEx | Accessed address | Storing to invalid address |
 | InvalidOpcode |  Loaded opcode   |  Executing invalid opcode  |
 |     Ecall     |       None       |     Ecall instruction      |
+
+# Assembly
+HoleyBytes assembly format is not defined, this is just a weak description
+of `hbasm` syntax.
+
+- Opcode names correspond to specified opcode names, lowercase (`nop`)
+- Parameters are separated by comma (`addi r0, 1`)
+- Instructions are separated by either line feed or semicolon
+- Registers are represented by `r` followed by the number (`r10`)
+- Labels are defined by label name followed with colon (`loop:`)
+- Labels are references simply by their name (`print`)