Bladder tumor is the most common tumor detected in patients presenting with gross hematuria. Early detection and treatment is crucial for good prognosis, however, delay in diagnosis and treatment is common. Routine work-up of gross hematuria includes cystoscopy and Computed Tomography Urography (CTU). If CTU has a high detection rate of bladder tumor, it can be used to direct further investigation of the patient, hopefully reducing delay to diagnosis and treatment. There is no consensus on which phase the bladder should be assessed at CTU. Assessment of the bladder in an early contrast-enhancing phase requires contrast material enhancement in bladder tumors and a bladder that is properly distended with urine. For patients younger than 50 years, the routine CTU protocol used for examining gross hematuria patients included unenhanced (UE), corticomedullary phase (CMP), and excretory phase (EP), with the start of the scan being enhancement triggered: patients aged 50 years or older followed the same protocol plus a nephrographic phase (NP). The CTU protocol was compared with flexible cystoscopy for detecting bladder tumors. Sensitivity for bladder cancer detection was equal for CTU and cystoscopy (0.87). Patients diagnosed with bladder cancer (n=50) were examined during UE, CMP, and EP, and 21 patients were additionally examined in NP. The highest mean tumor contrast enhancement was seen in CMP (37 HU). The CMP, NP, and EP in 106 patients were randomized into an evaluation order (n=318 different phases) and blindly reviewed by two uroradiologists. In CMP, sensitivity (0.95) and negative predictive value (0.99) were higher than in NP and EP. Four different preparation protocols for achieving bladder distension were compared. The protocol that included drinking 1 l of fluid during a two-hour period prior to examination without voiding during that period, gave satisfactory bladder distension without causing unacceptable patient discomfort and having the lowest compliance.   Gross hematuria patients should be primarily examined with CTU including UE, CMP and EP to direct further investigation of the patients. The patients should follow a preparation protocol including drinking 1 l of fluid during a two-hour period before examination and not voiding during that period.