SummaryThe electrophoreticβ-hexosaminidase pattern of Tay Sachs fibroblasts shows a large fraction, which correspond to the B fraction of normal material and a second fraction, which has the same electrophoretic mobility as the third fraction found in normal fibroblasts.The combined data of qualitative enzyme assays before and after heat inactivation and the electrophoretic pattern seem to give a reliable approach to the problem of detection of homozygote and heterozygote patients.