OBJECTIVES: We analyzed the influence of the radioactive fallout after the Chernobyl disaster on the rate and regional distribution of birth defects and abortion rates in southern Austria. STUDY DESIGN: During 1985 to 1989 a total of 66,743 births was monitored. Twelve sources provided data on 1695 cases of birth defects, 1579 of which were suitable for analysis. All cases were analyzed in terms of their calculated conception date and divided into three main groups according to their vulnerable phase of embryogenesis, spermatogenesis, and oogenesis. To study possible regional changes, the findings were plotted in 17 political subdistricts. The overall abortion rate and the counseling frequency at termination clinics was determined. RESULTS: No significant changes in the incidence of birth defects, abortion rate, or counseling rate at pregnancy termination clinics were observed. CONCLUSIONS: Assessing the teratologic potential of low-dose radiation is difficult and requires adequate grouping of birth defects, sufficient baseline data, and highly reliable registries.