We have previously suggested that fluid flow in the mouse exorbital lacrimal gland is driven by the opening of apical chloride and potassium channels. These ions move into the lumen of the gland and water follows by osmosis. In many tissues, the sodium potassium di-chloride cotransporter (NKCC1) replaces the chloride and potassium ions that move into the lumen. We hypothesize that mouse exorbital lacrimal glands would have NKCC1 co-transporters and that they would be important in fluid transport by this gland. We used immunocytochemistry to localize NKCC1-like immunoreactivity to the membranes of the acinar cells as well as to the basolateral membranes of the duct cells. We developed a method to measure tear flow and its composition from mouse glands in situ. Stimulation with the acetylcholine agonist carbachol produced a peak flow followed by a plateau. Ion concentration measurements of this stimulated fluid showed it was high in potassium and chloride. Treatment of the gland with furosemide, a blocker of the NKCC1 cotransporter, reduced the plateau phase of fluid flow by about 30%. Isolated cells exposed to a hypertonic shock shrank by about 20% and then showed a regulatory volume increase (RVI). Both the RVI and swelling were blocked by treatment with furosemide. Cells isolated from these glands shrink by about 10% in the presence of carbachol. Blocking NKCC1 with furosemide reduced the amount of shrinkage by about 50%. These data suggest that NKCC1 plays an important role in fluid secretion by the exorbital gland of mice.