This study was carried out on 68 cases (50 bilharzial stricture lower ureter, eight vesico-ureteral reflux cases and ten control). In cases of reflux associated with bilharziasis heavy ova-deposition was obvious all through the ureteral wall especially per-ureteral sheath. Also heavy deposition in the bladder wall involved the detrusor and trigonal muscle with fibrosis and obliteration of Waldeyer's space and atrophy and fasciculation of detrusor and trigonal muscle. This implies ureteral rigidity, impaired mobility and compression against a firm detrusor buttress.