Adiponitrile is an aliphatic dinitrile that is used as an intermediate in the synthesis of hexamethylenediamine. In order to asses potential health effects associated with industrial exposure, rats were exposed 6 h/d, 5 d/wk for 4 or 13 wk to atmospheres containing a range of adiponitrile concentrations and observed for signs of toxicity. A fertility assessment was also included as a component of the 13-wk study. Mortality and reduced weight gain were observed within 1 wk only in rats exposed to 493 mg/m3. Evidence of slight anemia was present in rats exposed to 99 mg/m3 and above. There was no histopathological evidence of organ toxicity in about 30 tissues from both sexes exposed up to 99 mg/m3, the highest concentration tested, for 13 wk. In addition, fertility, as monitored by reproductive performance and litter parameters, was normal in both males and females similarly exposed.