question: PURPOSE The optimal technique and mesh type for parastomal hernia repair have yet to be ascertained. Biologic meshes have been advocated in parastomal hernia repair due to purported resistance to infection in contaminated fields. The aim of this study was to evaluate the effectiveness of additionally cross-linked acellular porcine dermal collagen mesh (Permacol) for onlay parastomal hernia repair. METHODS A retrospective review of case notes, and abdominal CT scans when available, was performed for consecutive patients who had a parastomal hernia repaired between January 2007 and May 2010. All hernias were repaired with onlay placement of the biologic mesh. Hernias were classified according to the Moreno-Matias classification where CT scans were available. RESULTS Over a 34-month period, 30 consecutive patients, median age 74 years, 17 female, underwent parastomal hernia repair using onlay biologic mesh. There were 23 paracolostomy and seven paraileostomy hernias. The hernia was primary in 26 patients. Pre-operative CT scans were available in 18 patients (Moreno-Matias Type 1 = 1, Type 2 = 4, Type 3 = 13). There was one perioperative death, and 29 patients were available for follow-up, and median duration of follow-up (either CT or clinical) was 36 months (range 3-79). Twenty-six patients developed recurrence of the parastomal hernia (89.6%), and median time to recurrence was 10 months (range 3-72),with Moreno-Matias Type 1 = 0, Type 2 = 4, Type 3 = 14, unknown = 8. Fifteen out of 26 patients have had repairs of the recurrence using a variety of techniques. Of these, 10 patients have had further recurrence. CONCLUSION Onlay repair of parastomal hernia with cross-linked porcine dermal collagen biologic mesh reinforcement has poor long-term outcomes with unacceptably high recurrence rates and should not be performed.