The Glasgow Register of Congenital Anomalies reports the highest birth prevalence of congenital anomalies of all 18 participating centers in the EUROCAT project for the years 1980 to 1988. A high prevalence is found in most defect categories, with Glasgow in the top three places in the EUROCAT "league" in 7 of the 10 categories studied. While the high rate could reflect a high level of ascertainment, we have concluded that there is enough reason to be seriously concerned that the high Glasgow rate is a reflection of risk rather than methodology.