Male and female Sprague-Dawley rats were exposed nose-only for six hours per day for five consecutive days to commercial hexane at concentrations of 876, 3249 and 8715 ppm. Bone marrow cells, arrested in metaphase by colcemid treatment, were collected at 6 and 24 hours from the midpoint of the last exposure. Metaphase cells were examined microscopically for chromosome aberrations. No statistically significant increases in percentage of aberrant cells were observed in the commercial hexane-exposed animals, regardless of exposure concentration or bone marrow harvest time. The results of the assay indicate that under the conditions described in this report, commercial hexane did not induce chromosomal aberrations in bone marrow cells of male or female rats following inhalation exposure for five consecutive days.