Objective To investigate the bacterial colonization rate of the InterStim connector and lead during staged testing and the infectious outcome. Methods A total of 38 consecutive patients who were scheduled to undergo staged InterStim surgery were enrolled in the present prospective study. During the second stage procedure, immediately after the connector incision was opened, aerobic and anaerobic cultures were obtained by swabbing the connector pocket, the connector, and the permanent lead itself with sterile swabs. Results Of the 38 patients, 9 (24%) had a positive culture at the connector or lead site after the incision was opened during the second stage procedure. Of the 9 patients who had a colonized connector or lead, 3 (33%) subsequently developed device infection that required explantation. In contrast, only 3% of those who did not have colonization developed an infection afterward (P =.038). Longer percutaneous testing period was associated with a greater colonization rate. Of the 10 patients who underwent >14 days of staged testing, 5 (50%) developed connector and/or lead colonization. However, only 4 of the 28 patients (14%) who underwent ≤14 days of testing did so (P =.036, relative risk 3.5, 95% confidence interval 1.2-10.5). Conclusion The risk of InterStim colonization is significant using the staged, tined lead testing approach. Testing for >14 days between the 2 stages was associated with greater colonization rates. Patients should be evaluated on an ongoing basis during staged testing, with attempts to perform generator implantation once efficacy has been unequivocally demonstrated to reduce the risk of colonization.