Research documenting built environment effects on physical activity often excludes certain segments of the population. The senior population, one segment perhaps most influenced by the physical features of an environment, has been understudied. Developing reliable environmental measurements is an important component for increasing our knowledge of environmental effects on physical activity among seniors. The specific aims of this thesis include assessing the inter-rater and intra-rater reliability of the items on SWEAT; reducing the variables of SWEAT into summary concepts that describe the most important environmental factors impacting walking among seniors via principal components analysis; and comparing information gathered from SWEAT with qualitative observations collected simultaneously to determine if SWEAT was a complete instrument with which to assess the built environment.