The aim of this study was to compare the accuracy of bladder volume measurements using a portable ultrasound machine to measurement by catheterization. For 13 consecutive weeks, all patients admitted to the stroke unit at Royal Perth Hospital were studied by both methods when urinary retention was suspected. The accuracy of ultrasound bladder volume measurements and interobserver reliability were evaluated. Ninety ultrasound examinations were performed prior to catheterization, 70 were by one nurse, and 20 independently by two nurses. Correlation of ultrasound measurements with actual catheterized volume was highly significant (r = 0.983) as was interobserver reliability. The study showed that noninvasive bladder volume measurements using ultrasound are safe, effective, inexpensive and a useful adjunct to preventive bladder management and continence management in stroke patients.