The value of antimicrobial agents in the prevention of infections remains controversial. Penicillin prophylaxis of group A streptococcal infections has proved to be successful. Other forms of antibiotic prophylaxis as in open heart surgery or urinary catheter irrigations are used commonly, but are of uncertain value. Dr Waisbren has used antibiotics successfully to prevent infections in patients receiving TPN. The small doses of these three nephrotoxic drugs have been harmless to his patients, but perhaps could cause toxic effects if given over a long period of time, especially in the patient with renal insufficiency. The continued use of these drugs will encourage organism resistance, so my preference at this time is not to use prophylactic antibiotics and continue to advocate a controlled program of administration.