This study was designed to examine some of the psychosocial factors underlying the recent marathon boom. A survey of 459 marathoners varying in age, sex, ability, and experience was conducted to assess their reasons for running a marathon, the outcomes derived, and their experiences during a marathon. Information was also sought regarding the psychological aspects of running in general, particularly the concept of addiction to running. Measures of addiction to running produced a consistent pattern of sex differences, with females evidencing higher levels of addiction than males. With respect to reasons for running a marathon and perceived outcomes, some interesting trends were evident as a function of age. It was suggested that the attraction of the marathon to people of all ages and abilities may lie partly in its unique ability to satisfy a wide range of needs, both extrinsic and intrinsic.