BACKGROUND: Virtual reality (VR) is a potential tool for technical skills training. We tested the validity and instructional effectiveness of a prototype VR module for learning intravenous (IV) catheter placement. METHODS: First-year medical students (n = 37), third-year medical students (n = 14), and surgical residents (n = 9) attempted two pretest IVs into each other, used the VR module for 12 minutes, and subsequently attempted two posttest IVs. Success or failure were recorded for each attempt. For each successful attempt, time and global rating of IV insertion were also recorded. RESULTS: The pretest success rate was significantly different between groups (chi square = 28.71, P <0.01). VR success rate was not significantly different between groups (F2,57 = 1.47, ns). Although there was improvement in all groups during VR training (F2,114 = 44.16, P <0.01), this did not result in improvement in posttest performance. CONCLUSIONS: Significant differences between groups were observed in performance of IV insertion in physical reality. However, no significant difference was observed in performance in VR. Thus, performance in VR demonstrated neither construct nor concurrent validity. While performance improved in VR, transfer of skill from VR to physical reality was not observed. Additional development and testing of VR as a training tool is warranted before its widespread use can be recommended.