The presence of damage to the liver is one of the few conditions which are still considered to contraindicate the use of sulfonamide compounds or, at least, to require caution in their administration. Many clinical reports, however, include cases in which these drugs have been successfully used for the treatment of infections in the presence of jaundice of varying intensity and for patients with extensive damage to the liver. Adequate studies of the effects of this form of therapy on the hepatic function in such cases are few. In this paper there is reported a series of 37 patients who presented evidence of acute or chronic damage to the liver and who, for various reasons, received either sulfathiazole or sulfadiazine in full therapeutic doses. In each of their cases some studies were made in an attempt to determine the effect of the sulfonamide therapy on hepatic function.