In the human placental capillary endothelium, two cell types have previously been described with different organelle distribution patterns. This observation was based on examination of cross-sectional profiles. It is known, however, that organelle distribution may vary in different parts of a cell. The present study was undertaken to estimate morphometrically the pattern of organelle distribution in normal term placental capillary endothelium. Ten normal term placentae were processed routinely for electron microscopy. The volume fractions of the different organelles were determined in both the perinuclear and peripheral parts of the cells. In addition, comparisons were made between endothelial cells at the site of vasculosyncytial membranes (VSM) and those forming the remainder of the capillary wall (non-VSM). Multifactor ANOVA showed there was a significant difference between the perinuclear and the peripheral parts in the volume fractions of mitochondria, rough endoplasmic reticulum, intermediate filaments, all these being more in the perinuclear region, whilst vesicles and cytosol were more prevalent in the peripheral parts. In contrast, there was no significant difference between the regions of VSM and the non-VSM except for the volume fractions of microfilaments which were higher in the non-VSM region.