Macronuclear DNA s from three related hypotrichous ciliated protozoans were compared by agarose gel electrophoresis. Each was shown to be composed of DNA duplexes that yielded a unique pattern of bands overlying a continuous distribution of DNA sizes ranging from approximately 400 bp to approximately 20,000 bp. By EM, the number average molecular sizes for double-stranded DNA were 2,200 bp for Oxytricha sp., 2,514 bp for Stylonychia pustulata and 18,836 bp for Euplotes aediculatus. Contrary to previous reports we present evidence that the macronuclear DNA s in each of these three organisms lack single-stranded interruptions.