Abstract
Two different sizes of circular covalently closed deoxyribonucleic acid plasmids have been identified in four independent clinical isolates of Neisseria gonorrhoeae. All four strains contained a small plasmid with a molecular weight of 2.8 X 10-6 and two of the four stains also contained a large plasmid with a molecular weight of 24.5 X 10-6. The avirulent derivative of each of these four strains had the same plasmid complement as its virulent parent. There was no correlation between the presence of these plasmids and antibiotic resistance, piliation, and colony type associated with virulence, or ability to grow without seven specific amino acid supplements.