The optimum range for parathyroid hormone (PTH) levels in children with chronic renal failure (CRF) remains undefined. We aimed to determine growth velocity in children with CRF managed with normal PTH levels. We performed a retrospective case note review of 99 children (77 boys), with a glomerular filtration rate (GFR) <41 ml/min per 1.73 m(2), who had at least 2 years of 3-monthly follow-up. The age range at entry was 0.5-6.0 years; data collection was continued until 10 years of age or the commencement of growth hormone or renal replacement therapy. The median GFR was 22 ml/min per 1.73 m(2); over the study period mean serum calcium and phosphate levels were approximately equal to the mid-point of the respective normal ranges. Median PTH levels were equal to the upper limit of the normal range. Height standard deviation score (Ht SDS) at entry was -1.73. During the study period the overall mean change in Ht SDS was +0.3, significantly greater than the no change expected of a normal population ( P=0.004). The median dose of calcium carbonate was 150 mg/kg per day and 1-alpha calcidol 0.015 microg/kg per day. The growth rate was independent of all parameters, including age, PTH levels, the use of enteral feeds, and 1-alpha calcidol prescription. Our results indicate that catch-up growth can occur in infants and children with CRF when medical therapy is aimed at normalizing PTH levels.