Fifteen mature meadow voles (Microtus pennsylvanicus) were assigned to each of four diets: 1) basal; 2) basal + .001% pilocarpine (PLCN); 3) basal + .01% PLCN; 4) basal + .10% PLCN in a completely randomized design to measure the effect of PLCN on liver, kidney and parotid gland histopathology and feed intake. Meadow voles were fed each treatment for 14 d prior to euthanasia. Serum glutamic oxaloacetate transaminase, glutamic pyruvate transaminase and alkaline phosphatase levels were unaffected by dietary PLCN. Liver fresh weight tended to decrease with PLCN treatment, but kidney weight was not consistently affected. Parotid gland fresh weight decreased by 31% as the dietary level of PLCN increased from 0 to .10%. One of 15 voles on the control treatment died. Twelve of the remaining 14 voles showed no histopathological changes in the organs studied, but one showed segmental cystic dilation of some convoluted tubules and one showed chronic cortical interstitial nephritis. One vole of the 15 on the .001% PLCN treatment died. Eleven of the 14 remaining voles showed no histopathological changes in the organs studied, while two voles showed segmental cystic dilation of some convoluted tubules and one showed slight hydropic degeneration of hepatocytes. There was no mortality among voles fed .01% PLCN. Nine of the 15 voles showed no histopathological changes in the organs, while four showed slight hydropic degeneration of hepatocytes and one showed segmental cystic dilation of some convoluted tubules. Three of 15 voles died while fed .10% PLCN. The remaining 12 voles showed no histopathological changes in the above-mentioned organs, although three voles showed slight hydropic degeneration of hepatocytes.