Excess weight represents a critical and common health problem in Canada. The last survey of a national representative sample based on measured anthropometrics has been conducted in 1992. According to surveys using measured data, the prevalence of obesity (body mass index, BMI = 30.0 kg m(-2)) between 1970 and 1992 for those aged 20-69 years increased from 8% to 13% in men and 13% to 15% in women. The proportion of Canadians displaying a BMI > or =25.0 kg m(-2) increased from 47% to 58% in men and from 34% to 41% in women in the same period. The most recent prevalence estimates from self-reported data in a national representative sample indicated that 15% of the adult population (> or =18 years) was affected by obesity, while an additional 33% was classified in the overweight category (BMI 25.0-29.9 kg m(-2)) in 2003. However, it has been suggested that self-reported height and weight underestimate the prevalence of obesity by approximately 10%. Canadian children, aboriginal populations, and immigrants are some of the vulnerable groups particularly at risk of excess weight or for which the increase in the recent decades has been greater than the national increase. The increases in overweight and obesity over the past 30 years among Canadians have been dramatic. It will be possible to precisely analyse the current situation and its evolution in the last 10 years when data based on measured height and weight will be released, that is, in 2005 and after.