BACKGROUND The hypothesis of this study is that non-modifiable factors are more important in ventral hernia repair (VHR) surgical site infection (SSI) than care process factors. METHODS All VHR's which were reviewed retrospectively for both NSQIP-recorded data, and also: preoperative hospitalization, existing mesh, enterocutaneous fistula, open wound, case month, case day, case length, prophylactic antibiotics, skin preparation, other procedure performed, re-do operation, estimate blood loss, hernia size, repair approach, repair type, mesh used, skin closure, suture type, use of drains, and dressing. RESULTS 7% of 223 VHR's had an SSI. Factors associated with SSI: presence of mesh (24% vs. 4%), recurrent VHR (15% vs. 3%), operation time >120 min (15% vs. 3%), hernia size >200 cm2 (<25 cm2 2%, 26-200 cm2 4% and >200 cm2 11%), and EBL >100 ml (21% vs. 3%). Other factors did not affect SSI rates. CONCLUSION Factors associated with a more difficult operation were associated with SSI. Factors considered modifiable played limited roles. This has implications for choices of interventions made to reduce SSI rates.