Our study was undertaken to assess the inter- and intra-observer variability of the classification system of Sanders for calcaneal fractures. Five consultant orthopaedic surgeons with different subspecialty interests classified CT scans of 28 calcaneal fractures using this classification system. After six months, they reclassified the scans. Kappa statistics were used to analyse the two groups. The interobserver variability of the classification system was 0.32 (95% confidence interval (Cl) 0.26 to 0.38). The subclasses were then combined and assessment of agreement between the general classes as a whole gave a kappa value of 0.33 (95% Cl 0.25 to 0.41). The mean kappa value for intra-observer variability of the classification system was 0.42 (95% Cl 0.22 to 0.62). When the subclasses were combined, it was 0.45 (95% Cl 0.21 to 0.65). Our results show that, despite its popularity, the classification system of Sanders has only fair agreement among users.