63 male patients (64 knees) undergoing total knee arthroplasty (TKA) were randomized to receive treatment using either patient-specific cutting blocks - derived from 3D preoperative CT images - or standard instrumentation. The purpose of this study was to compare these two approaches with respect to component alignment and short-term clinical outcomes. Results at 6 months indicated that there were no significant differences between groups in regards to clinical outcomes or tibial and femoral component alignment. The number of outliers with respect to sagittal tibial alignment/slope was significantly greater when patient-specific guides were used.