The objective of this study was to describe the effects of fluoride on the epiphyses of the rat tibia by a newly developed histomorphometric technique for estimation of surface density and surface area of highly organized (anisotropic) organs: vertical section stereology. Seventeen experimental animals receiving drinking water with 100 ppm fluoride for seven weeks were compared with 16 controls. The proximal epiphyseal plate of the right tibia was examined. Morphometric estimates were obtained from vertical sections, i.e., histologic sections cut perpendicular to a defined plane. The thickness of the growth plate was significantly smaller in the fluoride group compared to controls (p < 0.05) due to a reduced thickness of the proliferative zone (p < 0.01). The surface density as well as the total volume of cells in the proliferative zone were significantly reduced in the fluoride group (p < 0.05). It was concluded that fluoride induces quantitative changes in the epiphyseal plate of the rat tibia probably by an effect on supracellular mechanisms.