An ultrasonographic urinary bladder morbidity score was developed and tested in 510 patients with schistosomiasis haematobia, and then evaluated for screening 1,134 randomly selected children from villages endemic for Schistosoma haematobium. The ultrasonographic urinary bladder morbidity score had four grades ranging from normal to marked thickening of the urinary bladder wall or any polyps or masses. Among both patients and randomly screened subjects, the ultrasonographic score was greater (P = 0.01 and P < 0.01) in males than in females. Children examined in the clinic had higher (P = 0.03) ultrasonographic scores than adults. Infected subjects in communities were more likely (P < 0.001) to have urinary bladder morbidity than uninfected subjects, and clinic patients with egg counts > or = 20 eggs/10 ml of urine had higher (P = 0.03) ultrasonographic urinary bladder morbidity scores than those with lighter infections. The geometric mean egg count was higher (P = 0.04) in clinic patients with grade II and III lesions than in those with grade 0 and I lesions. There was progressive improvement of the grade of urinary bladder morbidity scores in patients treated with praziquantel at each follow-up examination (P < 0.001) and there was a positive relationship (P < 0.01) between urinary bladder morbidity scores and ultrasonographic-detected renal back pressure changes. The ultrasonographic urinary bladder morbidity score objectively measured the severity of urinary bladder morbidity and correlated with intensity of S. haematobium infection in our subjects. It can be used in evaluating both morbidity in patients and in community surveys and in following the outcome of chemotherapy.