In this investigation of the long-term effect of mandibular protrusive function in children with severe Class II malocclusions, a group of children age 8 years 8 months were initially treated for 5 months with a headgear-Herbst appliance followed by a 3- to 5-year period of activator retention. The patients were studied out of retention at the mean age of 17 years 4 months and compared with an untreated control group. Part of the sagittal correction relapsed. As compared with the control group, the average 3.9 mm protrusive effect of treatment on the mandible decreased to a nonsignificant 1.5 mm out of retention. The significant 2.0 mm therapeutic increase of the condylion-gnathion distance decreased to 1.3 mm and was not significantly different from control values at age 17 years 4 months. However, the 1.5 mm posterior effect of treatment on the maxilla continued to increase during activator retention and the difference compared with the control group was 2.3 mm postretention. This effect on the maxilla partly compensated the relapse tendency observed in the mandible so that 3.8 mm of the 5.4 mm posttreatment sagittal improvement still remained out of retention. Because of the sample size and individual variability, the results should be interpreted cautiously, but the findings indicate that maxillary sutural remodeling might be more receptive long-term to orthopedic treatment than the mandibular condylar growth process.