Seventeen patients* (including three adults) with posterior urethral valves are presented with emphasis on the radiological findings. The characteristic findings on micturating cystourethrography are a transverse filling defect in the urethra with proximal dilatation and thinning of the stream distal to the lesion. Associated features are relative narrowing of the bladder neck and trabeculation of the bladder wall with the formation of diverticula in 50% of the cases.*Since the writing of the article, two more patients with posterior urethral valve have been seen, one child and one adult. Vesicoureteric reflux was observed in six patients. The upper urinary tract appeared normal on excretion urography in five cases, while in the others variable states of dilatation were observed. Follow-up examinations were useful in evaluating the results of treatment. It is concluded that micturating cystourethrography is the most useful radiological examination in the detection of posterior urethral valves. Excretion urography is essential for the evaluation of the upper urinary tract in all cases.