Infants born to mothers heavily exposed to polychlorinated biphenyls (PCBs) and dibenzofurans (PCDFs) have earlier been reported to have increased prevalences of natal and neonatal teeth. Some tendency toward higher prevalence figures of natal and neonatal teeth can be seen in the literature in normal child populations during the last 40 y. We therefore decided to determine the present prevalence of these teeth in a Finnish population and to evaluate whether infants with natal and neonatal teeth are more exposed to PCBs, PCDFs, and polychlorinated dibenzo-p-dioxins (PCDDs) than infants on average. A total of 34,457 infants born in 1997-2000 in four hospitals in southern Finland were examined for natal and neonatal teeth. The exposure of the infant to PCBs and PCDD/Fs was evaluated by measuring the levels of 17 most toxic PCDD/F and 36 PCB congeners in his or her mother's milk sample when the child was 4-8 wk old. A total of 34 infants had one or two natal (29 infants) or neonatal teeth (five infants). The milk analyses showed that the median level of PCDD/Fs as toxic equivalent (World Health Organization-recommended 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent quantity for PCDD/Fs in fat) was 11.9 pg/g in fat, and that of PCBs (World Health Organization-recommended 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent quantity for PCBs) was 7.24 pg/g in fat. These levels corresponded to the prevailing levels. The results showed that the prevalence of natal and neonatal teeth was 1:1000. No association was found between pollutant levels and occurrence of natal and neonatal teeth, indicating that the prevailing levels of PCDD/Fs and PCBs are likely to be below the threshold to cause perinatal eruption of teeth.