Starting in 1982, our laboratory has performed species identification of coryneform bacteria isolated from blood cultures, intravenous (i.v.) catheter tips and sites, urines with high colony counts, and other potentially significant cultures, using predefined criteria. Of 283 isolates identified, Corynebacterium jeikeium was the most common (47%), followed by CDC group G2 (12%) and C. minutissimum (8%). Blood cultures and i.v. catheter-related sources were the most frequent sources (58% of total). Certain species or groups, like CDC group G2, were most frequently isolated from blood or i.v. catheter sites. CDC group G2 showed a progression to greater multiple antibiotic resistance during this 9-year period. Occasional multiresistant strains of other species were also encountered. By in vitro testing, we note vancomycin remains the most active agent against corynebacterialike organisms, and is the most reliable antibiotic to use while awaiting susceptibility testing results.