A study of cytogenetic changes associated with formaldehyde (50000) exposure in mortuary science students was conducted. The study group consisted of 29 students, 22 males, average age 23.6 years, taking a course in embalming at a college of mortuary science. The subjects kept a record of their embalming activities for 85 days. Personal air monitoring for formaldehyde, glutaraldehyde (111308), isopropyl-alcohol (67630), methanol (67561), and phenol (108952) was performed. Buccal and nasal cavity epithelium and peripheral blood samples were collected before and after the first 9 weeks of the embalming laboratory. Buccal and nasal epithelial cells and blood lymphocytes were isolated and examined for micronuclei. The lymphocytes were scored for sister chromatid exchanges (SCEs). The subjects performed 144 embalmings during the 85 day period. This represented an average of 6.9 embalmings per student. Formaldehyde exposures varied from 0.15 to 4.3 parts per million (ppm), average 1.4ppm. The average embalming required 125 minutes. These data yielded an 8 hour time weighted average formaldehyde exposure of 0.33ppm, which was less than the OSHA standard, 0.75ppm. Estimated cumulative formaldehyde exposures ranged from 4.3 to 33.6ppm hours, average 14.8ppm hours. No glutaraldehyde methanol, phenol, or isopropanol was detected. The frequency of micronucleated buccal epithelial cells increased by 12 fold over the study period, a statistically significant increase. The micronuclei frequency in male but not female subjects, was significantly correlated with cumulative formaldehyde exposure. The frequency of micronucleated nasal cavity epithelial cells increased by 22% over the study period, a nonsignificant increase. The frequency of micronucleated lymphocytes increased by 28% and the frequency of SCEs decreased by 7.5%. Both changes were statistically significant. The authors conclude that low level exposure to formaldehyde vapor is associated with cytogenetic changes in buccal epithelial cells of the mouth and peripheral blood lymphocytes. The changes in peripheral blood lymphocytes indicate that effects can be induced in tissues distant from the area of initial contact.