Adherence of Pseudomonas aeruginosa to a Rabbit Cornea Cell Line (SIRC) cells in vitro was examined. Maximal adherence occurred at pH 5.0-7.0 and when the bacterial suspension at 1.4×10^9/ml was exposed to 2×10^4/ml SIRC cells at mid-logarithmic growth phase. Adherence was not affected by temperature. In the passage of time, a temporary rise of adherence occurred within 5 min of incubation and stationary phase was maintained from 30 min through 90 min of incubation. Killing of P. aeruginosa with heating at 65°C for 30 min or 60 min resulted in a marked decrease in adherence. Similar results were obtained by pretreatment of bacteria with 3% formaldehyde. Different strains of P. aeruginosa varied in their abilities to adhere to SIRC cells. Strains which produce protease adhered more avidly to SIRC cells than those which produce no protease, while the presence of pili was not correlated with bacterial adherence.