Background." Previously reported causes of renal pelvocalyceal thickening (PCT) include infection, acute tubular necrosis and obstruction. This study was performed to evaluate the significance of PCT noted sonographically in patients with hyperechoic native kidneys. Methods: We evaluated sonograms of 178 consecutive patients with hyperechoic native (excluding small and hydronephrotic) kidneys for the presence of PCT, and reviewed medical charts of patients with this finding. We also reviewed sonograms of two control groups: 20 consecutive patients with nephrosis unrelated to human immunodeficiency virus (HIV) infection who underwent renal biopsy, and 30 consecutive patients with severe hypoalbuminemia unrelated to kidney disease. Results: PCT was observed in 20 study patients with hyperechoic kidneys. HIV-associated nephropathy (HIVAN) was diagnosed in 15 patients (14 with bilateral PCT) in whom previously reported causes of this appearance were excluded. PCT was not observed in control patients. Conclusion: Renal PCT can occur in patients with HIVAN in the absence of HIV-related complications. PCT in HIVAN does not merely reflect nonspecific nephrosis or hypoalbuminemia. HIVAN should be considered if PCT is noted sonographically in hyperechoic kidneys, even in patients not clinically suspected of harboring HIV infection.