To ascertain the incidence of catheterinduced bacteriuria persisting after convalescence from urological operations, quantitative urine cultures were made three months or more after 78 operations (for prostatic obstruction, bladder tumors, or bladder stones) requiring indwelling catheters for two or seven days after operation. Only one patient showed quantitatively significant bacteriuria. In 24 of the patients the infection cleared up spontaneously. Antibacterial medication had been given to 23 patients while in the hospital, and 31 patients, including the one in whom infection persisted, received antibiotics afterward. Catheter bacteriuria does not necessarily persist after genito-urinary operations, provided factors favoring infection, such as stones and obstructions, are removed and provided patients are persistently observed to make sure that infections which do not disappear spontaneously are adequately treated.