More than 800 blood samples from members of 13 tribal groups in the northwest of Australia have been tested for 18 enzyme systems controlled by 21 loci and for haemoglobin. Two novel alleles, PGM121 and ACPF1, are each restricted to a single tribal population, suggesting relatively recent mutations. Other alleles conform very broadly with their distributions in other Australian Aboriginal populations. In particular, PGM32 maintains its inland distribution whilst PGDE and PEP B6 continue to be restricted to the north of the continent. Comparisons between tribes show the Baada to be distinctive, with high values of PGM21, GPT2, CA42 and ESD2 as well as having the novel allele ACPF1.