Twelve achondroplastic dwarfs underwent serial limb lengthening during childhood. All had repeated bilateral simultaneous elongation of their lower limbs. The height of these patients was plotted on growth curves for children with achondroplasia. The end results were evaluated after all patients reached skeletal maturity. Growth acceleration was seen in male patients with achondroplasia, but no such effect was seen in females. The female patients lost several centimeters as calculated from their predicted final height based on their preoperative growth curve and the centimeters gained by mechanical distraction. The authors' recommendation is to start limb elongation of male patients with achondroplasia at the age of 8 years or older, but to delay limb lengthening in female patients with achondroplasia until approximately 15 years of age to allow for maximal skeletal growth.