Objective. To develop an optically scannable food frequency questionnaire (FFQ), 'The Melbourne FFQ', suitable for classifying Australian-, Greek- and Italian-born individuals into quantiles of intake for a range of foods and nutrients. The FFQ would provide the primary measure of dietary exposure in a prospective cohort study. Design. The FFQ was modelled on that used for the (US) Nurses' Health Study. Food items were chosen on the basis of their relative contribution to the intake of a range of nutrients computed from weighed food records. Setting. Metropolitan Melbourne, Australia, a city of 3 million people, of whom 75.5% were born in Australia, 2.7% were born in Italy and 1.7% were born in Greece. Participants. Weighed Food Survey (1987-1989): A volunteer sample of 810 healthy middle-aged (40-69 years) men and women of whom 35% were born in Greece, 33% were born in Italy, and 32% were born in Australia. Melbourne Collaborative Cohort Study (1990-1993): A volunteer sample of 17 949 healthy men and women aged between 40 and 69 years of whom 61% were born in Australia, 21% were born in Italy and 17% were born in Greece. Results. A 121 item FFQ was developed, together with a customized nutrient database. The optical scanning format was generally well received with the majority of subjects requiring no assistance. The FFQ appeared to overestimate the consumption of fruit and vegetables. Conclusions. The Melbourne FFQ provides a convenient method of measuring habitual dietary intake in a large population setting. A separate study is required to assess how well the instrument characterizes diet at the level of the individual.