Sex differences and the effects of androgen on periodic acid-Schiff (PAS) positive substance in the submandibular gland of ICR strain mice were investigated with microspectrophotometry. The relative amount of PAS-positive groups per unit volume and per cell in the secretory tubule portion accorded with tubule-cell size which was larger in untreated male mice than in female or castrated male mice; PAS-positive groups increased following administration of testosterone propionate to female and castrated male mice. The relative amount of PAS-positive groups per unit volume in the acinar portion was larger in male mice and in the testosterone propionate-administered mice than in female or castrated male mice, though this difference was less pronounced than in the secretory tubules. However, no obvious difference was observed when the relative amount of PAS-positive groups per acinar cell was compared among these groups. The cause of the difference between the relative amount of PAS-positive groups per unit volume and per cell in the acinar portion may be attributed to the changes of cell size. The acinar cell size was smaller in untreated male mice and in the testosterone propionate administered mice than in female or in castrated male mice. It seems that androgen has little effect on the PAS-positive substance in the acinar cell, in contrast to its action on this substance in the secretory tubule cell.