Bacterial infections were studied in 51 immunosuppression kidney transplant recipients. Eighty infectious episodes occured in the first six post-transplantation months. Forty percent of these episodes were nonfebrile, detected during the routine bacteriological follow-up examination. Out of these 80 bacterial infections, 59 were localized (47 in the urinary tract, nine in the surgical wound and three in the lungs) and 21 had spread. Neutopenia occured in 13 patients, in association with septicaemia in eight of them. Usually septicaemia appeared before neutropenia. In 12 cases, infectious episodes (10 septicaemias and two localized infections) and transplant failure were closely related. The bacterial strains responsible for these infections were essentially: Staphylococcus spp (39), Streptococcus spp (14), Klebsiella pneumoniae (9), Escherichia coli (9). Most of the localized infections cleared up when treated with a specific antibiotic. Seven failures of antibiotic treatment were observed in 21 cases of generalized infections. The importance of regular post-transplantation bacteriological check-up in detecting and treating infectious complications in graft recipients must be emphasized.