Serum samples from people living in three villages (Simikot, Thymkyn and Yakba) in the Karnali River basin in extreme northwest Nepal and from people living in two villages (Dangrizong and Phalag) in the upper Kali Gandaki River basin in central Nepal were tested for the immunoglobulin allotypes Gm (1,2,3,5,6,10,11,13,14,17,21,24,26) and Inv(Km)(1). The people from one of the villages (Simikot) are Caucasoid in appearance and have cultural, linguistic and religious ties to southern Nepal and India. Those from the four other villages are Mongoloid in appearance and have cultural, linguistic and religious ties to Tibet. The Gm phenotype and haplotype arrays and Inv1 frequency for the samples from Simikot were, as expected, typically Caucasoid. The samples from Thymkyn and Yakba, on the other hand showed no evidence of being from Mongoloid and not Caucasoid individuals, except for the absence of Gm(3,5,10,11,13,14,26) samples. Their phenotypes could be explained by postulating either the Gm3,5,10,11,13,14,26 haplotype found among Caucasoids or the Gm1,3,5,10,11,13,14,26 haplotype found among Mongoloids. The latter is assumed to be present, because of the Mongoloid appearance of the donors of the samples. Larger numbers of samples, preferably from families, are needed to decide which of these alternatives is correct. The Gm haplotype and Inv1 frequencies of the samples from people in Dangrizong and Phalag villages are typically Mongoloid and significantly different from those for the samples from people in Thymkyn and Yakba. The frequencies for samples within the pairs of villages were the same. Whether these data indicate a cline or genetic drift can be determined on the basis of the comparison of data for samples from populations residing between the locations from which the samples were drawn for this study with samples from the two regions already studied. Larger numbers of samples from the two regions already studied are desirable and all samples should be analysed for additional polymorphisms.