In the subchronic inhalation toxicity study, four groups of male and four groups of female mice (20 mice per sex each for the control and high-concentration groups, and 10 mice per sex each for the low- and intermediate-concentration groups) were exposed to 0, 500, 2,000, or 7,000 ppm cyclohexane. Exposures were six hours per day, 5 days per week, for a total of 66 exposures per sex over a 14-week period. Mice were observed weekly for clinical signs before exposure and daily after each exposure. Group clinical signs and the response to an alerting stimulus were determined during each exposure in animals visible from the front of the chamber. Approximately half of the mice could be observed in each chamber during exposure. During daily observations of animals while they were in the chambers, abnormal behavior, interpreted as a potential neurological effect, was observed in mice exposed to 2,000 and to 7,000 ppm cyclohexane in a dose response fashion. Observed signs included hyperactivity in one or two mice visible from the front of the chamber in the 2,000 ppm group, and hyperactivity, circling, jumping/hopping, excessive grooming, kicking of rear legs, standing on front legs, and occasional flipping behavior in mice exposed at 7,000 ppm. In the 2,000 ppm group, hyperactivity first became apparent during the 64th exposure and continued until the end of the study. Abnormal behavior in the 7,000 ppm group was evident by the 4th exposure and continued throughout the remainder of the exposures. In addition, a diminished to absent alerting response was observed in mice exposed to 2,000 and 7,000 ppm cyclohexane.