The purpose of this study was to characterize response rates for mail surveys published in medical journals; to determine how the response rate among subjects who are typical targets of mail surveys varies; and to evaluate the contribution of several techniques used by investigators to enhance response rates. One hundred seventy-eight manuscripts published in 1991, representing 321 distinct mail surveys, were abstracted to determine response rates and survey techniques. In a follow-up mail survey, 113 authors of these manuscripts provided supplementary information. The mean response rate among mail surveys published in medical journals is approximately 60%. However, response rates vary according to subject studied and techniques used. Published surveys of physicians have a mean response rate of only 54%, and those of non-physicians have a mean response rate of 68%. In addition, multivariable models suggest that written reminders provided with a copy of the instrument and telephone reminders are each associated with response rates about 13% higher than surveys that do not use these techniques. Other techniques, such as anonymity and financial incentives, are not associated with higher response rates. Although several mail survey techniques are associated with higher response rates, response rates to published mail surveys tend to be moderate. However, a survey's response rate is at best an indirect indication of the extent of non-respondent bias. Investigators, journal editors, and readers should devote more attention to assessments of bias, and less to specific response rate thresholds.