The importance of endothelial cell swelling and subepithelial deposits in producing capillary wall thickening in women with pre-eclampsia is controversial. In this study renal biopsy tissue from 16 women with a diagnosis of pre-eclampsia was analyzed morphometrically. Women biopsied during pregnancy (N = 6) showed substantial, electron-dense subendothelial deposits in capillary loops, but these were rare or absent in women (N = 10) biopsied post-partum (P less than 0.01). Endothelial cell swelling was present in both groups of patients to an equal degree. Mesangial cell interposition occurred but was not the dominant feature, and was similar in both pregnancy and post-partum biopsies. The median percentage per patient occupied by basement membrane was similar for both groups. Subendothelial deposits appear to resolve early in the post-partum period.