Nine blood group systems of goats were identified using 12 caprine reagents produced by absorption of alloimmune antisera. The caprine C blood group system, possibly homologous to the ovine C blood group system, was characterized by two reagents and shown to be controlled by three alleles, C12, C25, and C-. A more complex blood group system of goats, designated G, was identified using three reagents and shown to be controlled by six codominant alleles (G10.19.20, G10.19, G10.20, G10, G19, G20) and a recessive allele (G-). A further seven one-factor two-allelic systems were identified by seven reagents. The nine genetic systems provided exclusion probabilities of 0.479, 0.492, 0.548, and 0.572 in Australian Angora, Dairy, Cashmere, and Texan Angora goat breeds, respectively.