This research describes the development and validation of measures designed to assess physical activity motivation and physical activity enjoyment across the adult lifespan. Two stages were used with samples of 259 and 275 adults respectively counterbalanced for age and sex. All respondents were currently engaged in a variety of sport and exercise activities and settings appropriate for all age groups. Stage one respondents completed an initial 50 - item physical activity motivation inventory and an initial 39-item physical activity enjoyment inventory. Results were used to identify factors and items for physical activity motivation and enjoyment that appeared consistent and stable across the adult lifespan in order to develop the Physical Activity Motivation Scale (PAMS) and the Physical Activity Enjoyment Scale (PAES). Alpha reliabilities were calculated for each sub -scale of the PAMS and PAES, and a convenience sample (n=40) completed the PAMS and PAES two weeks apart to determine test~retest reliabilities. Stage two respondents completed the PAMS, PAES, the short form of the Leisure Motivation Scale, the short form of the Leisure Satisfaction Scale, and the Center for Epidemiological Studies Depression Scale in order to confirm PAMS and PAES stage one factor structures, determine the convergent and divergent validity of the PAMS and PAES, and describe adult patterns of physical activity motivation and enjoyment across the lifespan. Additionally, results from stage two were used to distinguish between motivation for and enjoyment from physical activity. The Physical Activity Motivation Scale (PAMS) consists of 22 items and five sub-scales: Mastery and Autonomy, Social Recognition and Rewards, Affiliation, Family, and Self-Control. The Physical Activity Enjoyment Scale (PAES) consists of 14 items and sub-scales: Self Rewards, Social Recognition and Rewards, and Responsibility/Family. The PAMS and PAES sub-scales have acceptable internal consistency and testretest reliability, share expected variance with related constructs, and appear relatively stable and consistent across the adult lifespan. In stage two, the relationship between motivation and enjoyment in the physical activity setting was explored and preliminary support found for their cyclic, yet distinguishable natures. Directions for further research are proposed.