Diethyldithiocarbamate (DETC) and pyrrolidine dithiocarbamate (PDTC) were highly active against tubercle bacilli, with MICs of 8 mu g/ml and 0.13 mu g/ml, respectively. DETC and PDTC were active against old cultures, enhanced pyrazinamide or pyrazinamide/rifampin activity, and had serum inhibitory titers of 1:2 and 1:4, respectively, in mice given 100 mg/kg orally.