Accurate prevalence data on illnesses are of paramount importance for medical decision-making, healthcare planning, and the appropriate allocation of healthcare resources. When assessing the prevalence of any illness or health condition, it is important to base prevalence data on an assessment of the general population at large and not on selected groups of the population. Previous estimates of the prevalence of lower urinary tract symptoms (LUTS) have used postal surveys, telephone and in-person interviews, and, more recently, the Internet. Determining the mode of data collection for a research study is dictated by several factors, including target population, topic sensitivity, timeliness, and available resources. The purpose of this report is to document the rationale for conducting a large prevalence study of LUTS and its impact on patient outcomes using Internet- or Web-based surveys. A brief overview of important survey considerations is provided, and previous survey methods used in assessing the prevalence of LUTS discussed. The research objectives and sampling approach used in the EpiLUTS study in the USA, the UK and Sweden are presented, with a discussion of the advantages and disadvantages of this Internet-based sampling approach in relation to other epidemiological methods.