A number of serotypable E. coli, Salmonella and Shigella strains isolated from three districts in Kenya were investigated for carriage of plasmids. This was done through extraction of plasmids and separating them by electrophoresis on agarose. Most of the strains investigated showed presence of plasmids. The E. coli isolates had plasmids ranging in number from 1 to 5, the most common number was 2. The plasmid sizes ranged from 80 to 30 megadalton, the commonest of the heavy plasmids were 70 megadalton. The Shigella isolates had plasmids ranging in number from 1 to 3, the most common number was 1. The plasmid sizes ranged from 80 to 3.5 megadalton, the commonest of the heavy plasmids were 70 megadalton. Various plasmid-sizes have been published as being responsible for pathogenicity.