Because reliable maps are generally unavailable, we start by visiting each community to make a map and count houses. Each community volunteers to complete a census. Typically Siempre Salud completes a census in several days and utilizes one volunteer surveyor for every 1-2 square blocks. Siempre Salud trains surveyors (encuestadores) and manages the census and computer data entry of census results. A census enumerates all members of each household. Our goal is to account for everyone in at least 90% of houses. The census is a critical activity because we use it to form target groups (based on age and sex) for our various prevention and early detection programs.