Twenty-one types of mtDNA were found in a survey of 39 Israeli Jews, of whom 18 were Sephardic and 21 Ashkenazic. The survey was made with six restriction enzymes that together recognize an average of 600 bp/genome. The differences among the types appear to be due to base substitution at 19 cleavage sites, one deletion, and one conformational mutation. The numbers of differences imply that these modern Jews stem from a minimum of 21 maternal lineages that were already distinct from one another 4,000-5,000 years ago. In three of the four cases where a type was found in more than one person, it occurred in both Ashkenazic and Sephardic populations. The diversity of types in the combined sample of two Jewish populations is lower than both that in a sample from various parts of Africa and that in a sample from various parts of East Asia. Nevertheless, it is as high as that in a sample from diverse parts of New Guinea, an area much larger than that in Israel to which the Jewish population traces back.