One-hundred consecutive posterior cruciate retaining total knee arthroplasties were performed by one surgeon in 81 patients with an average age of 69 years. Diagnoses included osteoarthritis in 93 knees and rheumatoid arthritis in seven. The femoral alignment necessary to create a rectangular flexion gap was determined and compared with Whiteside's line, the transepicondylar axis, and a line in 3 degrees external rotation relative to the posterior condyles of the femur. The transepicondylar axis most consistently recreated a balanced flexion space whereas 3 degrees external rotation off the posterior condyles was least consistent especially in knees in valgus.