The Food Habits of Canadians Survey, conducted in 1997--1998 examined food and nutrient intakes of non-institutionalized adults aged 18--65 years (n = 1543) randomly selected from across Canada using the multi-stage random sampling strategy. Dietary intake was assessed by 24-h recall and a repeat interview was conducted in a sub-sample (n = 446). The overall response rate was 26%. Males, younger age adults (18--34 years), single persons and those with lower education levels were underrepresented in the study sample thus limiting the generalizability of the study results. Examination of the characteristics of the selected areas (n = 63) by response rates, indicated that areas with a higher percentage below the low income cut-off level, higher percentage who moved residence in the past 5 years and higher percentage speaking non-official languages as the mother-tongue were associated with low response rates. Additionally, areas with lower percentage females were associated with low response rates indicating that depending on the community characteristics different approaches may be needed to enhance response rates. Within- to between-subject variance ratios for several nutrients were higher when adjusted for age, gender, education, season, smoking and size of family compared to the crude ratios (e.g. for energy 1.07 vs. 0.49 for males). As a result, more days would be needed to reliably estimate usual intake once the data are appropriately adjusted. Examination of the within- to between-subject variability ratios for nutrients by smoking status indicated that the diet of smokers was no more variable than that of non-smokers. However, smokers had higher intakes of total fat (p < 0.05) and saturated fat (p < 0.05) and lower intakes of folate (p < 0.05) and vitamin C (p < 0.05). Smokers also had lower intakes of fruit and vegetables compared to non-smokers (p < 0.05). Given these differences, diet may be a confounder in studies examining smoking

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