About 70 individuals from Punjab were examined for some mtDNA polymorphisms, namely, the RFLPs of the six classical enzymes (HpaI, BamHI, HaeII, MspI, AvaII, and Hin-cII) and for the sites AluI(7,025), DdeI(10,394), and AluI(10,397). The AluI(7,025) polymorphic site was also investigated in 96 Indians from Uttar Pradesh and Andhra Pradesh and in 163 Mediterranean Caucasoids. Moreover, 30 Indian DdeI(10,394)Alu(10,397) (++) mtDNAs were typed by the "high-resolution restriction analysis" with 14 endonucleases to estimate their divergence time. The results obtained are the following: (1) The RFLPs analysis has displayed some Caucasoid types as in Indians of Uttar Pradesh; (2) the AluI(7,025) (-) allele, which defines the most frequent Caucasoid-specific lineage (haplogroup H), ranges from 18% to 45% in the Mediterranean Caucasoids, whereas it has shown low frequencies in Punjab (6.0%) and in Uttar Pradesh (1.8%) and was not found in Andhra Pradesh; (3) the DdeI(lO,394)AluI(10,397) (+ +) haplotype, which although previously was considered an East Asian marker (haplogroup M) and was found very frequently in India, is also frequent in Punjab (27%); this frequency is, however, much lower than in Uttar Pradesh (49%) and in Andhra Pradesh (74%), and a gradient decreasing from south to north is therefore observed; (4) the divergence time of the Indian DdeI(10,394)AluI(10,397) (++) mtDNAs has been estimated to be 30,250-60,500 years, a value that is compatible with that of the homologous East Asian lineage. These results strongly support the hypothesis that the DdeI(10,394)AluI(10,397) (++) haplotype predated the Indo-European invasion and probably the split between proto-Indians and proto-Orientals. Its frequency cline well reflects the major influence of Indo-Europeans in the north and in the center of India.