The growth-inhibitory effects of anthracene were determined against intestinal bacteria, and compared with those of its derivatives for a better understanding of structure-activity relationships. The Growth inhibiting activity was shown to vary the chemical, dose, and bacterial strain tested. In tests with Clostridium perfringens, anthracence evidenced strong () and moderate (++) growth inhibition at 1.0 and 0.25 mg/disc, respectively, but exhibited no growth inhibition effects against lactic-acid producing bacteria and E. coli. In our study of structure-activity relationships, anthracene-9-carboxylic acid evidenced strong () and moderate (++) growth inhibition at 1.0 and 0.25 mg/disc, respectively, but anthracence-9-carboxaldehyde, anthrone, and 9-(hydroxymethyl)-anthracene exhibited no growth-inhibitory effects against six intestinal bacteria. In conclusion, the growth-inhibitory activities of anthracene and anthracene-9-carboxylic acid against C. perfringens may be indicative of at least one of these pharmacological actions. Furthermore, anthracene and anthracene-9-carboxylic acid may prove useful as prospective therapeutics for the treatment of gastrointestinal diseases caused by C. perfringens.