The objective of this study was to explore the relationship between body mass index (BMI), its association with chronic disease, and its impact on health services utilization in the province of Newfoundland and Labrador, Canada, from 1998 to 2002. A data linkage study was conducted involving a provincial health survey linked to 2 health care use administrative databases. The study population comprised 2345 adults between the ages of 20 and 64 years. Self-reported height and weight measures and other covariates, including chronic diseases, were obtained from a provincial survey. BMI categories include: normal weight (BMI 18.5-24.9), overweight (BMI 25-29.9), obese class I (BMI 30-34.9), obese class II (BMI ≥ 35), and obese class III (BMI ≥ 40). Survey responses were linked with objective physician and hospital health services utilization over a 5-year period. Weight classifications in the study sample were as follows: 37% normal, 39% overweight, 17% obese, and 6% morbidly obese. The obese and morbidly obese were more likely to report having serious chronic conditions after adjusting for age and sex. Only the morbidly obese group (BMI ≥ 35 kg/m(2)) had a significantly higher number of visits to a general practitioner (GP) over a 5-year period compared to the normal weight group (median 22.0 vs. 17.0, P<0.05). Using multivariate models and controlling for the number of chronic conditions and other relevant covariates, being morbidly obese remained a significant predictor of GP visits (P<0.001), but was not a predictor for visits to a specialist or any type of hospital use. The increase in the prevalence of obesity is placing a burden at the primary health care level. More resources are needed in order to support GPs in their efforts to manage and treat obese adults who have associated comorbidities.