OBJECTIVE: To analyze and compare postoperative occurrences following ventral hernia repairs (VHRs) using mesh in clean-contaminated and contaminated wounds. BACKGROUND: Ventral hernia repairs using mesh is one of the most common surgical procedures performed. However, guidelines and outcomes of repairs in clean-contaminated or grossly contaminated ventral hernias have not been established. METHODS: Patients who underwent VHR with mesh between the dates January 1, 2005 and April 4, 2010 at all hospitals in the United States participating in the National Surgical Quality Improvement Program (NSQIP) were reviewed. Data from 33,832 patients were analyzed by field contamination level and then compared with data from patients who underwent VHR without mesh. Data were analyzed using the odds ratio test with a 95% confidence interval. RESULTS: The odds of having one or more postoperative occurrences were significantly greater in clean-contaminated and contaminated cases using mesh when compared with clean cases, with odds ratios of 3.56 (3.25-3.89) and 5.05 (1.78-12.41), respectively. There was a significantly increased risk of superficial surgical site infections (SSI) (2.53), deep SSI (3.09) and organ/space SSI (6.16), wound disruption (4.41), pneumonia (4.43), and sepsis (4.90) for clean-contaminated cases. Both clean-contaminated and contaminated cases had an increased risk of septic shock (5.82 and 26.74, respectively), and need for ventilator for more than 48 hours (5.59 and 26.76, respectively). In addition, there was a significantly increased odds ratio of complications in patients who underwent VHR with mesh (3.56) to nonmesh (2.52) in clean-contaminated cases. CONCLUSION: There is a significant increase in risk of postoperative occurrences following VHRs using mesh in clean-contaminated and contaminated cases relative to clean cases. We recommend avoiding the use of mesh in any level of contamination.