Ample empirical evidence suggests that prenotification is an important method to increase response rates in mail surveys. However, for Web-based surveys, the results on prenotification appear to be mixed. One explanation may be the lack of awareness of the initial e-mail contacts. For instance, automatic spam filters and unidentified senders of the prenotifications could lower the chance of the e-mail being noticed. To increase awareness when contacting participants for Web-based surveys, it might be more effective to send the invitations directly to the respondents’ cellular phones. This method seems most promising with younger persons in Germany, because this segment has near-universal cellular phone coverage. To compare the effectiveness of different prenotification procedures, we experimentally varied the initial contact mode in a fully crossed two-factorial design with (1) three different prenotification conditions and (2) two ‘invitation and reminder’ conditions. University freshmen were recruited for a Web-based access panel by completing a short paper and pencil questionnaire in a classroom setting consisting of basic demographics, psychographics, and questions about lifestyles. A total of 560 students were randomly assigned to one of the following experimental conditions: On the prenotification factor, one group received no prenotification at all, a second was contacted by mobile messaging (SMS) on their mobile phone, and a third group was contacted by e-mail, both announcing the prospective survey. For the survey invitation and reminder, respondents were randomly contacted either by e-mail or by SMS. Our paper will point out the influences of the experimental manipulations on various measures related to data quality. For example, response rates varied between 50% and 84% across the experimental conditions, with the combination of SMS prenotification and e-mail invitation performing the best. However, the use of SMS invitations led to quicker responses. Besides further elaborating on these results, we will also point out the influences of the experimental manipulations on sample composition and the responses to the substantive questions. Finally, practical implications for contacting participants of Web-based access panels in marketing and social research will be discussed.