This is the first report of sex reversal induced by injection of androgenic gland (AG) extract in brachyuran crabs. In the present study, the extract of AG from the mud crab Scylla paramamosain and the Chinese mitten crab Eriocheir sinensis was injected into newly developed female (i.e. just after sex differentiation) crabs E. sinensis. Masculinization was observed in the injection with E. sinensis as well as S. paramamosain. AG cross activity might exist between the two species. Sex reversal could be achieved at a low dosage of 0.14 (E. sinensis) or 0.06 (S. paramamosain) AG equivalent.