Objectives To examine the response to single-day intravenous pamidronate in a heterogeneous population with symptomatic osteoporosis. Study design Patients (n = 18) 6 to 21 years of age, meeting treatment criteria were offered treatment with a single-day infusion of pamidronate every 3 months. Baseline and follow-up data were recorded and compared between persons with risk factors of progressive chronic illness or ongoing glucocorticoid usage (group 1) and persons with neither risk factor (group 2). We also examined the association between changes in urinary N-telopeptide percentile and spinal bone mineral density (BMD). Results Spinal BMD Z score increased in all patients after 6 months of treatment. Although patients had an average of 1.9 fractures in the year preceding treatment, only 2 patients had fractures once treatment began. No significant differences in baseline data were noted between the two groups. However, group 1 had significantly less gain in BMD (P = .04) than group 2. No evidence of growth impairment was seen, and no association between changes in urinary N-telopeptide percentile and changes in BMD were noted. Conclusions Single-day intravenous infusion of pamidronate is efficacious and well tolerated in a heterogeneous group of pediatric patients with symptomatic osteoporosis. (J Pediatr 2003;142:417-23)