The presence of pili in human and animal parasites and pathogens of the genus Corynebacterium was examined. C. kutscheri, C. diphtheriae, and C. pseudodiphtheriticum possessed a fairly large number of pili, ranging from dozens to more than a hundred, in 91 to 100% of the bacterial cells. C. equi, C. hoagii, C. xerosis, C. pyogenes, and C. murisepticum had only a small number of pili in 10 to 37% of the bacterial cells. In C. bovis, C. striatum, and C. pseudotuberculosis, pili were detected in only 0.5% to 3% of the bacterial cells. The pili were similar to each other and to those of C. renale; they were not rigid and had a tendency to form bundles. The length of pili usually ranged from 0.2 to 3 mum, and their diameter was within a 2- to 6-nm range.