Acrylonitrile (ACN) and acrylamide (AA), structurally similar vinyl monomers, are both animal carcinogens. ACN is weakly mutagenic in bacteria and induces sister-chromatid exchange, unscheduled DNA synthesis and cell transformation in cells in culture. AA induces chromosomal aberrations in bone marrow, blood and germ cells in vivo, and dominant lethal mutations in the germ cells of male mice and rats. In the current study, the ability of AA and ACN to induce dominant lethal mutations in the germ cells of male Fischer 344 rats was compared. Three groups of 50 males were gavaged daily for 5 days with ACN (60 mg/kg in normal saline), AA (30 mg/kg in normal saline) or vehicle only; an additional group of 20 males received a single i.p. injection of 0.2 mg/kg triethylenemelamine (TEM) on the afternoon of day 5. Starting 1 day after exposure, each male was bred to one female per week for 4 weeks (TEM-exposed group) or 10 weeks (ACN, AA and control groups). Mating rates were reduced only during week 1 in the TEM-treated group; pregnancy rates were reduced only during week 2 in the AA-exposed group and week 4 in the TEM-treated group. Females were necropsied 13 days after the end of the appropriate mating week and the amount of pre- and post-implantation loss calculated. ACN treatment of male rats induced no increases in either pre- or post-implantation loss in females in any of the 10 weeks post-exposure examined.(ABSTRACT TRUNCATED AT 250 WORDS)