In the 50-year period since Fleming made his monumental discovery of penicillin, a vast array of anti-infective agents have been developed to combat the plethora of infectious microorganisms plaguing mankind. While once the ophthalmologist had only penicillin to resort to when faced with ocular infection, his choice now includes myriads of antibiotics. This variety of anti-infective agents has brought tremendous benefits, but it has also brought the need for greater knowledge on the part of the physician. He must be aware of newly introduced antimicrobial agents and reevaluate older drugs for new uses in the light of the development of tolerance and toxic side effects.