Proteinuria selectivity index (PSI) was determined in 54 Saudi children with nephrotic syndrome whose renal biopsy showed minimal change in 13 and non***-minimal histologic changes in 41 patients. The selectivity was determined with two pairs of proteins, IgG/transferrin and IgG/albumin. There was considerable overlap in the values of PSI in patients with minimal and non-minimal histological changes. The clinical utility of PSI in differentiating minimal change nephrotic syndrome and non-minimal change nephrotic syndrome is low.