Comparison of questionnaire information and pharmacy data on drug use.

Information on chronic drug use at any time in the past was collected with a self-administered questionnaire as part of a prospective cohort study on diet, other life-style factors and cancer among subjects aged 55-69 years. The validity of the questionnaire information on drug use was evaluated among 207 subjects by comparing it to pharmacy records of dispensed drugs. The comparison could be made for the 2.