Response rates to surveys are decreasing. The purpose of this study was to evaluate the use of lottery tickets as incentives in an epidemiologic control group. A self-administered questionnaire was sent to parents in the municipality of Stockholm, Sweden, who were to be used as a control group in a study addressing stress in parents of children with cancer. A stratified random sample of 450 parents were randomized into three incentive groups: (a) no incentive; (b) a promised incentive of one lottery ticket to be received upon reply; (c) a promised incentive of one lottery ticket to be received upon reply and an additional lottery ticket upon reply within 1 week. The overall response rate across the three groups was 65.3%. The response rate was highest in the no incentive group (69.3%) and lowest in the one plus one lottery ticket group (62.0%). In a survival analysis, the difference between the two response curves was significant by the log-rank test (P = 0.04), with the no incentive group having a shorter time to response than the incentive group. Our findings suggest that the use of lottery tickets as incentives to increase participation in a mail questionnaire among parents may be less valuable or even harmful. Incentives may undermine motivation in studies in which the intrinsic motivation of the respondents is already high.