The results of 32 total knee arthroplasties performed for osteoarthritis in 32 patients who were 40 years of age or younger are reviewed. At a mean followup of 7.9 years (minimum, 5 years), the Knee Society knee scores increased from an average of 47 to 88 points, and the function scores increased from 45 to 70 points. Overall, Knee Society knee scores were considered good or excellent in 82% of patients (26 knees) and fair or poor in 18% (six knees). Postoperative function scores were good or excellent in only 40% (13 knees). The average postoperative flexion arc was 110 degrees. If patients involved in worker's compensation cases are excluded from analysis, the results improved substantially, with range of motion averaging 113 degrees, and Knee Society knee scores and function scores averaging 92 points and 77 points, respectively. Excluding the five patients involved in workmen's compensation cases, knee scores were good or excellent in 91% of patients (25 knees) and function scores were good or excellent in 50% of patients (14 knees). Three revisions were performed for aseptic failure; one additional patient has radiographic evidence of tibial loosening, representing an aseptic failure rate of 12.5% at 8 years. Although slightly higher than observed in older patients, this failure rate still may be considered acceptable for this population of patients with severely affected knees who are not considered candidates for nonarthroplasty surgery. Despite a slightly higher tendency for aseptic failures in this group of patients, cemented total knee arthroplasty may provide some patients younger than 40 years of age with severe debilitating and recalcitrant osteoarthrosis, an important option with reasonable mid- and long-term results.