The effects of promethazine were studied in children with frequently recurring pyelonephritis which was not associated with urological abnormalities. The results of three methods of treatment were compared: 10 children were given a combination of gentamycin and promethazine for 7 days (Group 1), 11 received gentamycin treatment alone for 10 days (Group 2), and 19 (Group 3) were on long-term oral antibiotic prophylaxis (5.6 +/- 2.1 years) with episodes of intensive treatment of recurrences. In a 3-year follow-up period, the number of pyelonephritis recurrences was significantly lower in Group 1 than in Groups 2 and 3. Six out of 19 children in Group 3 had renal scarring. The authors suggest a synergistic effect between gentamycin and promethazine therapy. Promethazine increases antibiotic sensitivity, which could contribute to the elimination of recurring urinary tract infections.