The rising popularity of online surveys in marketing research precipitates a flood of e-mail invitations requesting participation from potential respondents. As a result, response rates are diminishing, reflecting a decline in the willingness to participate in web surveys. To compare the effectiveness of different response-enhancing techniques in a list-based web survey, an experiment with a full factorial between-subjects design varying the factors sender, number of contacts, and questionnaire layout was set up. A total of 1,563 members from a list of information technology (IT) managers employed at Austrian companies were assigned randomly to one of eight experimental conditions. Their willingness to participate was measured in terms of total response and break off. The results indicate that using a prenotification message and a female sender for contacting male sample members increases response rates; using an advanced questionnaire layout significantly reduces break offs, but does not influence total response.