A mating between Black Orpington bantams produced, in addition to blacks, a single female in which the black colouration was replaced by dark chocolate. 2. A mating of the chocolate-coloured female with a black male, F2 and backcross matings demonstrated that the chocolate phenotype is caused by a recessive sex-linked gene to which I assign the symbol *CHOC. 3. A mating of "chocolates' inter se yielded all chocolate offspring.