Trends in antibiotic prescribing can be examined by a review of data from dispensed prescriptions and from antibiotic certification records of the Food and Drug Administration (FDA). Prescription data on selected oral antibiotics and anti-infectives were obtained from IMS America's National Prescription Audit. Data compiled between 1965 and 1977 show increasing use until 1973—with a plateau thereafter—for antibiotics judged by physicians to be relatively “safe,” namely, the erythromycins, ampicillin and other penicillins, and the cephalosporins. Tetracycline use, although rising until 1973, declined somewhat thereafter, perhaps because of increasing concern with dental staining in children. Sulfonamide use has declined steadily since 1965, presumably for safety reasons. Use of clindamycin was nearing a level similar to that of cephalosporin use until 1975, when its risk of precipitating severe colitis, including pseudomembranous colitis, became well-known. The FDA's antibiotic certification records show that the volume of injectable cephalosporins and gentamicin administered has increased steadily and as of 1977 was still rising.