Web surveys are an efficient data collection mode if surveys are sent out within an organization. While the survey period is shorter compared to other modes and can provide results sooner, web surveys generally suffer from low response rates. Numerous studies have been conducted on increasing response rates in web surveys using incentives, reducing length, multiple contacts, and alike. However, the work on how the subject line of the invitation email affects the likelihood of participation is limited. One study reports that for groups less attached to the study sponsor, there was a significant difference in subjects’ participation when different subject line contents were used. The respondents with high attachment to the sponsor did not show any significant differences in participation across different subject lines (Porter & Whitcomb, 2005). Another study shows a difference in favor of email subject lines that are in a “plea” rather than an “offer” format (Trouteaud, 2004). Survey fatigue has been an increasing concern for the field of survey research. Researchers at Children’s Hospital Boston/Harvard Medical School receive numerous web survey invitations per month. One such survey is the Children’s Hospital Boston’s Clinical Research Program annual service satisfaction survey. Using this survey we implemented a 2x2 experiment with regard to the subject line of the invitation email. We hypothesized that the use of the word “survey” itself in the subject line diminishes the likelihood of participation because of the participants’ survey fatigue. We also expected to replicate Trouteaud’s results with respect to the use of “plea” versus “offer” format in the invitation email’s subject line. The participants were randomly assigned to each of the four conditions. This study, therefore, allows us to examine if the content of the subject line of the invitation email to a web survey influences the likelihood to respond.