BACKGROUND The treatment of femoral shaft fractures in heavier children has been studied extensively, however, no study has directly compared elastic nail (TEN) and rigid locking nails (RLN) in this population. Our goal was to compare TEN with RLN in length-stable diaphyseal femur fractures in heavier children and adolescents (47 to 85 kg) using weight-matched cohorts. METHODS We retrospectively reviewed records for length-stable diaphyseal femoral fractures treated with TEN or RLN over 8 years at our Level 1 Pediatric Trauma Center. Perioperative and follow-up data, including total charges for care, were recorded and radiographic images were reviewed. These data were used to create 2 cohorts having each patient in the TEN cohort matched to within 2 kg of the corresponding patient in the RLN cohort. RESULTS Fifteen patients from each cohort could be weight matched (TEN, 60.8 kg vs. RLN, 60.4 kg). The RNL cohort was older (15.4 vs. 13.5 y; P = 0.005). Time in operating room and estimated blood loss were greater in the RLN cohort: 158 versus 220 minutes (P = 0.003) and 42 versus 182 ml (P = 0.003), respectively. All patients had a full range of motion at the latest follow-up. Complications were observed in 6 of 15 TEN and 10 of 15 RNL (P = 0.14). Implant-related problems were more common in RLN patients, but this was not statistically significant (3 of 15 vs. 9 of 15; P = 0.06). In the TEN cohort, malunion and leg length discrepancy (> 2 cm) each occurred in a single patient (20 degrees varus, 2.3 cm shortening, respectively) compared with 0 of 15 in RLN (P = 0.48). Treatment with TEN resulted in a total charge of $742 more than RLN (P = 0.75). CONCLUSIONS In our weight-matched comparison, the use of TEN resulted in decreased time in operating room, estimated blood loss, and implant-related problems. Malunion and leg length discrepancy remain of concern when heavier patients are treated by TEN, but were not significantly increased relative to RNL in this study.