Plasmodium falciparum has two extrachromosomal genomes, the mitochondrial 6-kb DNA element and the 35-kb circular DNA. The mitochondrial gene cytochrome b on the 6-kb element has been shown to be inherited uniparentally. In order to ascertain whether the route is maternal or paternal we have examined preparations of male and female gametes of the closely related Plasmodium gallinaceum for the presence of extrachromosomal DNA. DNA from purified preparations of gametes was hybridised to probes for both the 6-kb and 35-kb extrachromosomal genomes. Both probes hybridised to the preparation of Plasmodium gallinaceum female gametes but not to that of the males. We conclude that the extrachromosomal DNAs of malaria parasites are transmitted maternally.