Although in Crohn's disease post-operative recurrence is common, the determinants of disease recurrence remain speculative. The aim of this study was to examine factors affecting post-operative recurrence of Crohn's disease. A Medline-based literature review was carried out. The following factors were investigated: age at onset of disease, sex, family history of Crohn's disease, smoking, duration of Crohn's disease before surgery, prophylactic medical treatment (corticosteroids, 5-amino salicylic acid (5-ASA) and immunosuppressants), anatomical site of involvement, indication for surgery (perforating or non-perforating disease), length of resected bowel, anastomotic technique, presence of granuloma in the specimen, involvement of disease at the resection margin, blood transfusions and post-operative complications. Smoking significantly increases the risk of recurrence (risk is approximately twice as high), especially in women and heavy smokers. Quitting smoking reduces the post-operative recurrence rate. A number of studies have shown a higher risk when the duration of the disease before surgery was short. There were, however, different definitions of 'short' among the studies. Prophylactic corticosteroids therapy is not effective in reducing the post-operative recurrence. A number of randomized controlled trials offered evidence of the efficacy of 5-ASA (mesalazine) in reducing post-operative recurrence. Recently, the therapeutic efficacy of immunosuppressive drugs (azathioprine and 6-mercaptopurine) in the prevention of post-operative recurrence has been investigated and several studies have reported that these drugs might help prevent the recurrence. Further clinical trials would be necessary to evaluate the prophylactic efficacy of immunosuppressants. Several studies showed a higher recurrence rate in patients with perforating disease than in those with non-perforating disease. However, evidence for differing recurrence rates in perforating and non-perforating diseases is inconclusive. A number of retrospective studies reported that a stapled functional end-to-end anastomosis was associated with a lower recurrence rate compared with other types of anastomosis. However, prospective randomized studies would be necessary to draw a definite conclusion. Many studies found no difference in the recurrence rates between patients with radical resection and non-radical resection. Therefore, minimal surgery including strictureplasty has been justified in the management of Crohn's disease. In this review, the following factors do not seem to be predictive of post-operative recurrence: age at onset of disease, sex, family history of Crohn's disease, anatomical site of disease, length of resected bowel, presence of granuloma in the specimen, blood transfusions and post-operative complications. The most significant factor affecting post-operative recurrence of Crohn's disease is smoking. Smoking significantly increases the risk of recurrence. A short disease duration before surgery seems, albeit to a very minor degree, to be associated with a higher recurrence rate. 5-ASA has been shown with some degree of confidence to lead to a lower recurrence rate. The prophylactic efficacy of immunosuppressive drugs should be assessed in future. A wider anastomotic technique after resection may reduce the post-operative recurrence rate, though this should be investigated with prospective randomized controlled trials.