A follow up study, to replicate and expand an earlier study on the developmental toxicity of 2-methoxyethanol (109864) (2ME) in combination with exposure to radiofrequency (RF) radiation, was conducted. Virgin female CD-Sprague-Dawley-rats were irradiated on gestation day nine or 13 in the dominant electric field mode under continuous wave conditions at a frequency of 10 megahertz (MHz). A two factor design was used with five levels of 2ME (0, 75, 100, 125, and 150mg/kg) and five levels of RF radiation (sham exposure or colonic temperature maintained at 42 degrees-C for 0, 10, 20, and 30 minutes). No material toxicity was noted from 2ME administration. In groups where RF radiation maintained the colonic temperature at 42 degrees for 30 minutes, 20% died within 1 to 2 days after exposure. Day nine exposure produced little evidence of interaction between 2ME and RF radiation. 2ME produced few malformations; RF radiation accounted for virtually all of the malformations observed including external, skeletal, and visceral malformations. Day 13 exposure produced significant malformations in the groups exposed to 2ME, RF radiation, and 2ME plus RF radiation. Forepaw malformations were the predominant malformations induced. Statistical analysis failed to show a global synergistic effect, but did indicate a synergistic effect at intermediate levels of the dose ranges. The authors suggest that the threshold for interactive effects lies below 75mg/kg. Future research which defines the lowest effect level of interaction between 2ME and RF radiation will facilitate a more accurate risk assessment for worker exposure.