Endogamous populations belonging to Brahmin, Vysya, Mala, and Madiga castes of Andhra Pradesh, South India, were investigated for certain red cell enzyme and serum protein genetic markers. Frequency values were statistically analyzed to assess genetic variation among the populations. Average heterozygosity of ten loci and genetic diversity within and between the populations were calculated by using the methods of Nei. Nei's index was used to calculate genetic distances between the pairs of populations. A dendrogram was drawn adapting the modified unweighted pair group method suggested by Li, which agreed with the history of the populations.

The distribution of C3 phenotypes was studied in some endogamous caste groups of Andhra Pradesh, South India. The C3F allele was found to be at a low frequency and comparable to those found in castes of other regions on the Indian subcontinent.

The distribution of glyoxylase (GLO) I phenotypes in six endogamous subgroups of Brahmins and in the Mala and Madiga castes of Andhra Pradesh was investigated. The GLO I gene frequencies ranged from 0.2444 to 0.3575. The frequency of 0.3565 found in the Mala is the highest recorded on the Indian subcontinent.

The distribution of acid phosphatase (ACP) phenotypes in six endogamous Brahmin sub-sects and in the Vysya, Mala and Madiga castes of Andhra Pradesh, India, were investigated. The ACP A gene frequency ranged from 0.167 to 0.254. The ACP C allele was observed in three Brahmin sub-sects.

The distribution of the C₅ isozyme of the serum cholinesterase (E₂ locus) was studied in several endogamous Hindu caste groups and Muslim sub-sects of Andhra Pradesh in South India. Both intra and inter population variation was marked with a comparatively low incidence of C₅ in the populations studied.