New mobile communications technologies provide a unique opportunity for innovation in public health surveillance. Smartphone Web access is immediate, accessible, and confidential, a combination of features that could make it ideal for ongoing surveillance. The purpose of this study is to evaluate the process and outcomes of conducting a population-based survey through Web surveys with smartphone respondents. The study consists of an initial telephone interview to identify smartphone users followed by 2 weekly surveys completed via smartphone. We will determine the following: 1) technological feasibility: whether and under what circumstances smartphones can be used to collect population-based public health and behavior data; 2) quality of the data: evaluating response bias, coverage bias, outcome rates through comparisons of data collected by smartphones vs. landline & cell phones from another survey; 3) cost effectiveness: how much smartphone data collection costs compared to more conventional data collection approaches. As mobile communications continue to evolve, a better understanding of how smartphones can be used to collect data is critical to public health surveillance.