The safety and efficacy of performing concomitant surgical procedures with an incisional hernia repair (IHR) is not well understood. There are conflicting reports on the outcomes for permanent mesh implantation in the setting of clean-contaminated procedures. The purpose of this study was to review the effect of concomitant surgical procedures on IHR outcomes. This is a retrospective multisite cohort of patients undergoing elective IHR at 16 Veterans Affairs hospitals from 1998 to 2002. Concomitant procedure status, hernia characteristics, and operative details were determined using physician-abstracted operative notes. Hernia outcomes of recurrence and mesh explantation were determined from the medical chart. χ(2) tests, Kaplan-Meier curves, and Cox regression were used to evaluate the effects of concomitant status on hernia outcomes. Of the 1495 elective IHRs, 75 (4.8%) were same site and 56 (3.8%) different site concomitant procedures. At median follow-up of 69.3 months (range 19.1-98.3), 33.6 per cent of patients had a recurrence, mesh explantation, or both. Permanent mesh placement was less likely among concomitant procedures as compared with nonconcomitant procedures (P < 0.0001). Adjusted Cox proportional hazards models of hernia outcomes resulted in an increased hazard for recurrence among same site clean procedures (Hazard Ratio (HR) = 1.8, P = 0.03) and an increased hazard for mesh explantation among same site clean-contaminated procedures (HR = 8.4, P = 0.002). Concomitant same site procedures are significantly associated with adverse hernia outcomes as compared with isolated IHR or IHR with other site concomitant procedures. The high failure rate of hernia repairs among same site concomitant procedures should be taken into account during the surgical decision-making process.