The efficacy of cephalexin compared to that of ampicillin has been studied in 92 children with urinary tract infections (UTI). In 26 patients more than one UTI was treated, the total number of infections treated being 118, 59 with cephalexin and 59 with ampicillin After cephalexin treatment 49 cases (84.5%) gave pathogen-free urinary samples compared to 37 cases (62.7% after ampicillin. Eseherichia coil was absent in the post-treatment urine samples of 33 patients out of 36 (91.6%) treated with cepha lexin and in 22 out of 40 patients (55.0%) treated with ampicillin. No side-effects to cephalexin were reported compared to an incidence of 15% in patients receiving ampicillin