Although apprenticeship served surgeons in training well a hundred years ago, the complexity of surgical technology in the 21st Century has exponentially increased the demands on surgical education. Pelvic trainers can provide the necessary basic training for endoscopic and laparoscopic surgeons, but it usually is necessary to incorporate live-animal or cadaver practice or both to train fully in today's complex procedures. Advances in computer and materials technology have allowed the development of realistic simulators, but validation studies are required. Reliability is the reproducibility and precision of the test or testing device. Validity measures whether the simulator actually is teaching or evaluating what it is intended to teach or measure. Face validity relates to the realism of the simulator; content validity is a judgment of the appropriateness of the simulator as a teaching modality. Criterion validity compares the evaluation results from the new simulator with those of the old technique. The two types of criterion validity are concurrent - the extent to which the simulator correlates with the "gold standard" - and predictive - the extent to which the simulator predicts future performance. Construct validity indicates whether the simulator is able to distinguish the experienced from the inexperienced surgeon. For competency assessment, performance on a simulator should predict, or at least correlate with, an individual's performance in the operating room. A variety of endourologic models and simulators have been described, but only a few have been subjected to validity testing. An even greater number of simulators has been developed for laparoscopic skills training, but none is dedicated to training for laparoscopic urology. Surgical simulation must be used within an effective learning environment, underpinned by knowledge and professional attitudes.