Population data for the transferrin variants in the South Australian and Camden Park strains of the Australian Merino [sheep] are reported. In all, 5 variants designated A, B, C, D, and E were distinguished. The relationship between these variants and those reported in previous investigations of the Merino and other breeds was determined In 2 of 6 samples there were significant departures from Hardy-Weinberg expectations. Closed blocks with small effective population size, Camden Park and 1 South Australian (Roseworthy) flock, had fewer than 5 variants, the number generally found in all strains of the Australian Merino examined so far. For the Roseworthy material it was possible to demonstrate that the parent population, Anama, had the 5 variants. The 2 Roseworthy flocks derived from the Anama stock had significantly different gene frequencies from that flock.