This paper is based on two random sample trials with nearly 3,000 students in each trial (2009 and 2010 fall) which demonstrates that there are predictable drop-off points for questionnaires delivered over the Internet to a random sample of students. The questionnaire was designed to elicit alcohol, tobacco and drug-related behavior and attitudes as well as demographic information. The data suggests that in both the years the drop off rate reached 11% at the same point in the questionnaire. This point in the questionnaire was the 13th screen in a 29 screen questionnaire. After that, the drop off rate would plateau at 15% in both the years. The data also suggests that among those who dropped off, nearly 50% dropped off within the first five minutes of opening the questionnaire and the drop off would plateau about 30 minutes into the questionnaire by which time nearly 91% of the total number of drop offs had left the questionnaire. The same trend was observed in both years of the study. These findings suggest that it is useful to ensure that respondents can be offered some incentive to stay with the questionnaire when they are about half way through a long questionnaire. The fact that drop offs plateau near the half-way point is important to consider to reduce the overall drop off amount. It is also important to ensure that the respondent be offered some incentive to stay with a questionnaire within the first five minutes of opening the questionnaire. This could reduce the drop off rate significantly. Further analysis of the nature of questions and formatting of questions merit additional examination to locate other predictors of drop off.