A case of Serratia marcescens endophthalmitis following an intracapsular cataract cryoextraction in a diabetic patient is delineated. Appropriate antibiotic therapy failed to control the infection. Intravitreal administration in rabbit eyes of the culture of live bacteria, broth suspension of the dead-disrupted form of the organism, or the bacteria-free culture filtrates produced an infection that mimics the case presented.