Isolated bladder rupture has an insidious presentation which results in delayed diagnosis and management. Forty-four patients, of mean age 33.3 years, were seen over a period of 7 years. There was a history of trauma in 33 patients, although this was minor in 20. Alcohol intoxication, head injury or paraplegia could have led to lack of sensation of the distending and subsequently injured bladder in 18 patients. The mean delay between an identifiable incident or presentation and diagnosis was 5.4 days. The mean admission or preoperative levels of blood urea and creatinine were raised to 19.6 mmol/l and 362 mumol/l respectively in those with a delayed diagnosis. The diagnosis was made by voiding cystourethrography in 36 patients and by laparotomy in eight. When blood urea and creatinine concentrations are increased in a patient with an ill-defined abdominal ailment and a history of trauma or drunkenness, ruptured bladder should be considered.