Fifty four consecutive total knee arthroplasties were reviewed to compare the accuracy of extramedullary versus intramedullary tibial resection guides. An extramedullary guide ( Group I ) was used in 25 cases and an intramedullary guide ( Group 2 ) was used in 29 cases. Group 1 system included the LCS knee system and Group 2 system included the Whiteside Ortholoc Advantim total condylar knee system. Preoperatively, the two groups were similar, with no statistical significant differences observed in diagnosis, alignment, and patient age. Postoperative tibial component alignment angles were similar in both group (Group 1, 0.8degrees varus; Group 2, 1.1degrees varus ). In group 1, 84% of tibial components were aligned within 2degrees of the 90degrees goal and in group 2, 83% of tibial components were aligned within the same range ( p > 0.05 ). In all cases, an intramedullary guide was used to prepare the distal femur. In femorotibial angles, with group 1 averaging 4.2degrees valgus versus 4.7degrees valgus in group 2 (p > 0.05). If the optimal femorotibial angle was defined by the range from 5±2, it was achieved in 76% in Group 1 and 72% in Group 2 ( p > 0.05 ). This study demonstrates no significant differences between the extramedullary and intramedullary group not only in optimal tibial component alignment angle but also in optimal femorotibial angle. This means that each system is satisfactory for the tibial side, but it is more important for the surgeon to appreciate that the indications, potential limitations and sources of errors are unique to each system and to decide which system to use according to the particular case in question.