Objective: To survey the associations between several risk factors and birth defects, in order to detect potential new teratogens. Methods: Data of the two Dutch European Registration of Congenital Anomalies (EUROCAT) registries collected before January 1, 1998 were used to perform X 2 tests for a large number of risk factors and birth defects. Defects caused by chromosomal or monogenic disorders were analyzed separately. Results: Cross- tabulations of 80 groups of birth defects with 303 risk factors were studied. Of these, 126 combinations had a p value under 0.05, and 34 had a p value under 0.001. Of these 34 associations, some are known in the literature, some were found before in the same databases and some were new associations. Conclusions: This is a good method for generating new hypotheses for associations between risk factors and birth defects. It can be a start for new, more in-depth studies of potential teratogens. Copyright (C) 2000 S. Karger AG, Basel.