This retrospective case review of 43 children with primary nephrotic syndrome was designed to evaluate the relationship among renal ultrasound findings at presentation, subsequent corticosteroid responsiveness and histological diagnoses. Fifty-one percent of patients had abnormal sonograms; nephromegaly was present in 42% and increased renal echogenicity in 35%. There was no relationship between nephromegaly and either response to corticosteroids or specific glomerular lesions causing nephrosis. Although the presence of echogenic kidneys did not denote a particular type of renal disease, it was significantly more frequent in corticosteroid-resistant than in corticosteroid-responsive patients (62% vs. 18%, P < 0.05). We conclude that increased renal echogenicity at time of presentation is a possible indicator of corticosteroid resistance in children with primary nephrotic syndrome.