The aims of the study were to assess the prevalence of birth defects (BDs) among different occupational groups and non-working parents, and to identify possible risk factors associated with BDs in Singapore live births born between 1 January 1994 and 31 December 1998. To do this, information on live births (from the Singapore National Registry of Births and Deaths) and BD cases [from the National Birth Defects Register (NBDR)] was obtained from 1 January 1994 to 31 December 1998. There were a total of 237 755 live births in Singapore between 1 January 1994 and 31 December 1998. Over the same period, 3293 cases of BDs were reported to the NBDR, giving an overall rate of 13.9 per 1000 live births. A downward trend with time was noted. Of the live born with BDs in this series, 36.7% presented with multiple anomalies. The overall occurrence of malformation (per 1000 live births) among working versus non-working mothers was 13.4 versus 14.2, respectively, and 13.8 for working fathers compared with 16.8 for non-working fathers. Parents in the occupational group 'Legislators, Senior Officers & Managers' had the lowest prevalence rates of congenital anomalies (9.4 per 1000 for mothers and 10.3 per 1000 for fathers), while the 'Agricultural & Fishery Workers' had the highest rates (40.0 per 1000 for mothers and 23.4 per 1000 for fathers). However, the very small number of workers in this latter group makes the rate unreliable. The prevalence of BDs in Singapore is comparable to those in other countries. Parental work per se is not correlated with BDs.