The peripolar cell was described in the glomeruli of sheep by Ryan et al. in 1979 and these cells have subsequently been detected in many species (Ryan et al. 1982; Gall et al. 1986; Hanner et al. 1980). The peripolar cells are located at the junction between the podocytes of the glomerular capillaries and the epithelial lining of Bowmann's capsule, encircling the hilar region of the glomerular tuft. Functionally, the peripolar cells have been considered to be a part of the juxtaglomerular apparatus but the precise nature of the cells has not been identified (Gardiner et al. 1985). Recently, it has been found that an antibody against rat urinary kallikrein reacts positively with sheep peripolar cell (Gall et al. 1984). This finding has led to the suggestion that the peripolar cells may influence the renin secretion through the kallikrein-kinin system. In our experiments with long-term low-calcium condition accompanied with hyperplasia of juxtaglomerular cells the peripolar cells were easily detected. The results suggests that the increase in the number of peripolar cells is closely related to the hyperplasia of juxtaglomerular cells.