The antibacterial activity of some xanthate derivatives K(SSCOR), where R = C6H5-(CyX), CH3NHCH2CH2-(MAEX), (CH3)2NCH2CH2-(DMAX), (CH3)2NCH2CH(CH3)-(DMAIX) and (C2H5)2NCH2CH2-(DEAEX) together with their diorganotin (IV) complexes R2Sn(SSCOR)2, where R' = Me, Bu(n), Ph, has been studied against eight species of bacteria in vitro. A significant activity against S. typhimurium was displayed by the xanthate derivative CyX and its complex Ph2Sn(CyX)2 at concentrations ranging from 1-10 micrograms/ml, and a remarkable activity was exhibited by the complexes Ph2Sn(CyX)2, Ph2Sn(MAEX)2 and Ph2Sn(DMAX)2 against P. aeruginosa at concentrations ranging from 0.1-10 micrograms/ml. By contrast, no such activity was demonstrated by the antibiotics used in this study (amoxicillin and chloramphenicol) against the same bacterial species.