X-ray microanalysis was carried out on resting and stimulated rat exorbital lacrimal gland. The acinar cells of the resting gland are rich in calcium, which is localized in the secretory granules. In vitro stimulation with the cholinergic agonist carbachol leads to decreased cellular concentrations of K and increased concentrations of Na and Cl, concomitantly with intracellular vacuole formation. In vivo stimulation with pilocarpine leads after 90 min to loss of virtually all secretory material and also of the major part of the intracellular calcium. The secretory material is replenished after 24 h, and calcium levels in the acinar cells are then comparable to those in the resting gland. Chronic pilocarpine treatment induces significantly elevated calcium levels in the acinar cells of rat lacrimal gland.