Since none of the studies of long-term management of recurrent urinary tract infections considered the possibility of patients' not taking medication, compliance with long-term antibiotic therapy was tested by urine check in 93 children with recurrent urinary tract infection. Only 30 children (32.2%) took the prescribed drugs at regular intervals, 27 children (19.1%) did not take the antibiotics at all and 36 patients took the drugs irregularly, skipping one or two doses a day. The difference in infection rate between regular takers (3.9/year) and non-takers (7.2/year) and irregular takers (4.8/year) and non-takers was statistically highly significant. Forgetfulness and negligence of the parents was found to be the main reason for not giving the child the medication. Treatment studies which show the advantage of one regimen over another or which try to define optimal duration of therapy should take particular care in evaluation compliance.