The authors carried out a prospective study and also looked at the literature in order to assess the contribution ultrasound makes in the diagnosis of the aetiology of upper urinary tract infections in pregnancy. They studied two matched series (patients and controls). They note that ultrasound is reliable in the aetiological diagnosis of upper urinary tract infections without complications and they discuss its place and the contribution it can make as compared with more invasive investigations of infections of the upper urinary tract in pregnancy (such as I.V.U. and C.T. scanning).