Heel cord advancement(HCA), which has been applied for the correction of equinus deformity in spastic cerebral palsy, has some theoretical advantages. However, HCA has also theoretical disadvantage that the procedure remove the tensile force exerting to the calcaneal apophysis. In order to evaluate the effect of HCA on the calcaneal growth, we compared the changes of calcaneal and foot lengths between the operated feet and non-operated feet after HCA. Among the 54 patients who had been treated with HCA at Seoul National University Childrens Hospital from March 1990 to August 1995, we excluded the cases who had been treated bilaterally, and also excluded hemiplegic patients in whom the ipsilateral feet were already shortened and the growth rates are different between the ipsilateral and contralateral foot. Seven patients who met the criterior of this study were included for the evaluation. There were 3 diplegics and 4 paraplegics, and average age at operation was 10 years and 6 months(range; 7 year 8 months-16 year 5 months). Average follow-up period was 3 years and 5 months(range; 2 years-4 years 9 mos). Total calcaneal lengths, anterior and posterior part of calcaneal lengths were measured on the standing lateral radiographs of the foot and ankle. Ratios of the operated limb over the non-operated limb were calculated for the three parameters. Ratios of posterior part of calcaneal lengths decreased significantly(P=0.031). Ratios of total calcaneal lengths decreased and ratios of anterior part of calcaneal lengths increased. However, the changes of two ratios were not significant. Ratios of posterior part calcaeal lengths over total calcaneal length decreases significantly(P=0.016). In conclusion, HCA can cause calcaneal growth retardation, especially posterior part of calcaneus, due to removal of physiologic tensile force of Achilles tendon.