Summary—In a 1‐year laboratory‐based study the validity of certain findings on microscopy and culture of mid‐stream urine specimens as predictive of the presence of structural or functional abnormalities of the urinary tract was tested. During 1986, infection was diagnosed in 12,705 specimens sent to the laboratory by general practitioners; in the light of the findings a comment suggesting the possibility of underlying urinary tract pathology was appended to the reports of specimens from 652 patients. Data were available from the investigation of 233 of these patients. The percentage in whom abnormalities were detected considerably exceeded that reported from studies of bacteriuric children and of adult women with symptoms. It is suggested that the use of these criteria may assist clinicians to select, from the very large number of patients who suffer from urinary tract infection, those who require invest