The response of physicians to a mailed questionnaire: a study in Ontario, Manitoba and British Columbia.

During 1965, 1585 questionnaires were sent to physicians in British Columbia, Manitoba and Ontario to elicit information about persons who had died and in whom a chronic non-specific respiratory disease had been recorded on the registration of death. The response rate to the first letter of enquiry was 54.1%. This was improved to 76.5% when the enquiry was sent by registered mail, and to 90.6% by a registered special appeal. The final response rate was 93.8% for British Columbia, 92.8% for Manitoba and 89.5% for Ontario. Although response varied with the time of the year, there was no evident relationship between response rate and characteristics of the physician. Physician characteristics studied were place and year of graduation and the nature of practice. Acceptable and high response rates to mailed questionnaires eliciting clinical data from physicians can be obtained if the investigator's concern is demonstrated by sending the request in successive waves to the diminishing group of non-respondents.