Prepaid monetary incentives consistently exert the largest positive effect on response rates in mail surveys. For web-based surveys, it has not been possible to administer monetary incentives via the Internet in advance. Recently, several new web-based services have been introduced that can transfer money to people online. Does this really have the same positive effect on response rates as shown in traditional mail surveys? The authors investigated this question experimentally in the context of a web-based survey among members of a professional association in Virginia. The results indicate that prepaid incentives in web surveys seem to have no advantages concerning the willingness to participate, actual completion rates, and the share of incomplete response patterns when compared with postpaid incentives. Furthermore, postpaid incentives show no advantages over no incentives. Finally, compared to no incentives, prize draws increase completion rates and also reduce various incomplete participation patterns.