THA in young patients is challenging regarding restoration and survival because patients are young, active, and tend to have disturbed anatomy. We asked whether a three-dimensional custom cementless stem could restore hip function, decrease osteolysis and wear, and enhance stem survival in young patients. We retrospectively reviewed 212 patients (233 hips) younger than 50 years (mean, 40 years) at a followup of 5 to 16 years (mean, 10 years). The Merle D'Aubigné-Postel and Harris hip scores improved at last followup. No thigh pain was recorded for any of the patients; 187 of the 212 patients (88%) had full activity recovery, 206 had full range of motion, and 151 had a score greater than 80 points for all five categories of the Hip disability and Osteoarthritis Outcome score. Five patients had femoral osteolysis not associated with pain. With revision for any reason as an end point, the survivorship was 87% (range, 77%-97%) at 15 years, and considering stem revision only, the survivorship was 93% (confidence interval, 90%-97%) at 15 years. Our data compare favorably with those from series using standard cementless stems at the same followup with a high percentage of patients achieving functional restoration and a low rate of complications.