In the micronucleus study, one group of five male (control) and one group of 10 male (test) rats were exposed whole-body to 1,5-cyclooctadiene (COD) vapor for six hours/day for two days at 1500 ppm at 0 ppm. During exposures, rats in the 1500 ppm group exhibited depression at absence of an alerting response mainly during the latter half of the daily exposures, and incoordination was evident in three of 10 rats during the first exposure. Immediately after exposures, all rats in the 1500 ppm group exhibited lethargy. All test rats displayed incoordination after the first exposure, and two of 10 rats exhibited abnarmal gait after the second exposure. No clinical signs of toxicity were evident the day after each exposure.