We reviewed 36 cases of culture-proven Bacillus species ocular infections occurring between September 1974 and December 1989. Kirby-Bauer disk sensitivities were available in 34 of the 36 cases (95%). All Bacillus species isolates were sensitive to the aminoglycoside antibiotics (N = 34) and to vancomycin hydrochloride (N = 32); resistance to clindamycin was found in four of 18 (22%) of tested isolates. Although B. cereus was uniformly sensitive to these antibiotics, resistance to clindamycin occurred in four cases in the non-B. cereus group. The microbroth dilution technique confirmed the Kirby-Bauer data. The aminoglycosides were uniformly effective, but the cephalosporins (first, second, and third generation drugs) were consistently ineffective against B. cereus and varied from sensitive to moderately sensitive for the non-B. cereus isolates. Our microbiologic laboratory findings suggest that vancomycin hydrochloride in combination with an aminoglycoside ensures more consistent antibiotic coverage of Bacillus species ocular infections.