Epidemiological studies have suggested that spontaneous abortion may be increased in medical personnel following the sort of chronic low-level exposure to the anesthetic gas nitrous oxide (N2O) seen in surgical or dental operatories. These results are supported by some, but not all, animal studies, and results are less well established at low exposure levels. Behavioral effects in exposed animal offspring have also been observed, but again not in all studies. To further examine this problem, we conducted the present experiments. Adult male or female rats were exposed to trace concentrations of N2O (0%, 0.1%, 0.5%, or 1.0% in air) for 6 h daily either throughout gestation (females) or for 9 weeks (males). Offspring from treated adults were subjected to an extensive behavioral test battery. There were no clear dose-response effects on any of eight behavioural tests for any offspring. Maternal and offspring weights were normal from conception through adulthood. Additionally, we studied effects of N2O on male fertility by mating treated males with untreated females and examining uterine contents. There was no evidence for a substantial decline in fertility of exposed males, although there was a small dose-related trend for resorptions to increase and live births to decrease with increasing paternal N2O exposure. There results suggest that there is little alteration in male or female fertility following chronic exposure to low levels of N2O. There are also no significant long-term behavioral alterations in offspring exposed gestationally to trace levels of N2O via dam or sire.