In this paper we present the electron microscopic analysis of two distinct extramitochondrial circular DNA species in the fission yeast Schizosaccharomyces pombe (S. pombe). Both DNA species can be isolated from mitochondrial fractions, but disappear after DNase treatment of mitochondria, demonstrating their extramitochondrial location. The size of these molecular species is 3.08 ± 0.18 μm and 2.00 ± 0.09 μm (standard deviation). They are present in a ratio of approximately 9:1 in the DNA preparations analyzed. 