OBJECTIVE To assess whether in prepubertal children insulin secretion is pulsatile as in adults and to study the influence of body weight on the pattern of insulin secretion. METHODS Insulin profiles were obtained by 4-min sampling for 2 h, starting at 08.00 a.m. after an overnight fast in 10 prepubertal obese children (BMI-SDS 4.9 +/- 1.6) and in 6 healthy age-matched controls. Five of the obese children were also studied after weight reduction (Delta BMI-SDS 1.6 +/- 0.4). The data have been analyzed by the Pulsar program. RESULTS Obese children had higher mean insulin levels, insulin secretory areas under the curve above 0 (AUC0), and AUC above baseline (AUCb), with more frequent peaks of larger amplitude and duration compared to controls. Following weight reduction there was a normalization of AUC0 and mean insulin levels while AUCb, peak frequency, amplitude and duration did not change significantly. Correlation analysis revealed that BMI-SDS was strictly related to the parameters of pulsatile insulin secretion such as AUC0, AUCb, mean insulin level, peak amplitude and peak frequency. CONCLUSIONS Insulin secretion in children is pulsatile and its secretory pattern is influenced by body weight.