Size and charge selectivity of capillary permeability in the salivary glands of nephrotic children were investigated by measuring salivary excretion of endogenous plasma proteins of different size and charge. We examined 10 children with steroid-sensitive nephrotic syndrome (SSNS) in relapse and subsequent remission, 11 with steroid-resistant nephrotic syndrome, and 11 healthy children (controls). Albumin [mol. wt. 66 kilodaltons (kDa), isoelectric point (pI) 4.9] was measured by radio-immunoassay, transferrin (mol. wt. 77 kDa, pI 5.9) and immunoglobulins IgG1 (mol. wt. 150 kDa, pI 7-9) and IgG4 (mol. wt. 150 kDa, pI < 6) by enzyme-linked immunoabsorbent assay. In saliva, no significant differences were found between the four groups of children for any of the four proteins. Also, the saliva/plasma ratios of the four proteins were not different among the four groups. From these data, we conclude that in subjects with SSNS in relapse, neither size nor charge selectivity of salivary gland capillary permeability are affected.