Tail biting is a behavioural problem with both welfare and economic consequences. Various conditions that may contribute to tail biting have been identified in a number of research reports. This paper examined those reports and extracted these causative factors. A weighting factor was developed for each of these contributing conditions, and a model developed to estimate the risk of tail biting in any housing/management system. The ability of the model to predict the relative level of tail biting in two environments was assessed using treatment comparisons reported in 12 scientific papers. In total, 77 pairs of treatments were assessed, and in 63 of these comparisons the model predicted the relative level of tail biting correctly. From this the authors conclude that the model may be a useful tool in assessing the risk for tail biting in pigs. Additional testing, with provision for further modification of the model, is required.