Two hundred five strains comprising 16 Campylobacter species, subspecies, or proposed groups were examined for phenotypic characteristics useful in identification. All strains tested were oxidase-positive, gram-negative rods that failed to oxidize or ferment glucose. The tests most valuable for identification at the species or subspecies level were catalase, hippurate hydrolysis, reduction of nitrate and nitrite, production of H2S in triple sugar iron agar slants, growth at 25°C, sensitivity to nalidixic acid and cephaiothin, urea hydrolysis, and growth in semisolid medium containing 1% glycine or 3.5% NaCI. Some deviation from previously published results