The phenotypic arrays for seven erythrocyte antigenic systems of a sample of the Melbourne population were found to be distributed according to Zipf's Law. A simple model of heterozygote selective advantage was unable to account for the excess of observed frequencies of arrays over those expected under the random-mating hypothesis. Persons with (ccDEe, MMss) were over-represented and those with (A1, MNSs P1--) were under-represented in the sample.