For patients less invasive image-based procedures (IBP) such as laparoscopy have many benefits in comparison to traditional open surgery, such as less pain, faster recovery, and fewer scars. However, to perform IBP effectively, efficiently, and above all safely, the surgical team is highly dependent on technology. The interaction with the surgical instruments and equipment requires extensive training. The proficiency level of the physician and the interaction with the instruments and equipment are key factors in ensuring quality of surgical performance in IBP and patient safety. During surgery, the surgeon should be able to concentrate on the therapeutic tasks. To achieve this, the gap between the preferred and actual level of proficiency of the physician should first of all be minimised by means of preclinical training using simulation tools. In this thesis, the validity of virtual reality simulators for training and assessment of basic psychomotor skills for laparoscopic surgery and flexible lower gastrointestinal endoscopy (colonoscopy) is established. The relation between different IBP skills was also investigated. The performance on two basic laparoscopy tasks (bimanual tissue manipulation and angled laparoscope navigation) proves to be not related; clinically-based expertise in laparoscopic tissue manipulation does not infer skilfulness in angled laparoscope navigation. Training in basic laparoscopy tasks does not affect performance of basic colonoscopy tasks (and vice versa). Training and assessment of basic IBP skills should thus focus on each IBP skill type independently. The influence of specific characteristics of the simulator interface on the efficacy of preclinical training on simulators was also studied. The angled laparoscope navigation task is performed better in an abstract virtual environment than in a virtual environment with simulated anatomic landmarks of the abdomen. And, for training of laparoscopic suturing tasks haptic feedback is a prerequisite. Furthermore, the quality of performance and patient safety should be better safeguarded by improving the interaction with the instruments and equipment in the operating room. Using an integrated operating room system together with the prototype of Pro/cheQ (a digital integrated procedural checklist tool) reduces the number of equipment and instrument related risk sensitive events further than using only an integrated operating room system.