Recognizing the problem posed by diabetes mellitus, the National Diabetes Commission was created by Republic Act 8191 in 1996. The Commission identified the need for a Second National Diabetes Survey to have an updated estimate of the magnitude of the disease in the country and to have the needed information for developing a diabetes prevention and control program. This paper reports the prevalence of diabetes mellitus and impaired glucose tolerance (IGT) in adults and the factors associated with the prevalence of these conditions. A cross-sectional population-based study assessed the occurrence of diabetes and impaired glucose tolerance among a random sample of 7044 adults, aged 20-65 years who were residents of urban and rural areas in Luzon. Blood glucose level was measured by OGTT using the current WHO criteria. The crude diabetes prevalence of 5.1% represented a 54% increase over the figure (3.3%) for a similar population in Luzon in 1982. An increase was also noted in the magnitude of IGT which almost doubled from 4.1% in 1982 to 8.1% in the present survey. Only one in three diabetics reported that they had diabetes. The frequency of diabetes and IGT in urban and rural areas were about the same, although a substantial increase from the earlier survey was noted in rural areas. Women registered a higher prevalence for both conditions than men. Aside from age and gender, the other correlates of diabetes mellitus were hypertension, family history of diabetes, WHR, BMI, and physical inactivity. IGT had similar correlates as diabetes except physical inactivity. The present findings which are consistent with those of other studies underscore the role of lifestyle behaviors in diabetes and should be the target of intervention to prevent further increase in disease frequency. © 2003 Elsevier Ireland Ltd. All rights reserved.