Phenotype and gene frequencies for four blood group systems (ABO, MN, Rh and P) and haptoglobin among five endogamous groups of Delhi, India, are reported. All the systems are polymorphic in all the population groups. The average heterozygosity per locus in high (in the range 48-52 per cent) for all the groups. The extent of genic variability among the groups in terms of net codon differences per locus has been studied; the heterogeneity within the groups is large as compared to the between-group heterogeneity. There is no definite clustering of the of the groups with respect to their biological rank.