Response rates in mixed-mode studies are lower when mail and Internet modes of survey response are offered at the same time (Griffin, Fischer, & Morgan 2001; Israel, 2009; Messer & Dillman, 2010). There is also evidence that the final sample in mixed-mode studies is more representative than the final sample in mail-only studies (Messer & Dillman, 2010). Yet, there is some evidence that offering a Web response option in mixed-mode studies can lead to a lower overall response rate (Griffen, et al., 2001); furthermore, survey costs increase with offering more than one mode of response. Using an experimental design for both a telephone survey and a mail survey, both with prenotification letters where half of the sample is offered a chance to complete on the web and half are not, we evaluate the costs and benefits of the following on final response and cooperation rates: (1) sending a prenotification letter with the opportunity to complete the survey via the Web; (2) sending a renotification letter informing people that they will be contacted in the near future; and (3) not notifying people prior to contacting them to participate in a survey.