Several aspects of obligatory running are examined with particular emphasis on the anorexia analogue hypothesis. The psychometric characteristics of the Obligatory Exercise Questionnaire were examined in a preliminary study. The OEQ is unrelated to socially desirable responding and has adequate reliability and validity. Data were collected from a second sample to identify obligatory and nonobligatory runners. Validation of the obligatory construct is examined by comparing demographic and training differences between obligatory and nonobligatory runners. Obligatory runners train more miles, days, and hours per week; have faster finishing times; are more likely to continue running when injured; and report feeling higher levels of anxiety when not running. The anorexia analogue hypothesis is examined by comparing the personality characteristics of obligatory and nonobligatory male marathon runners. Obligatory and nonobligatory runners were not significantly different on measures of identity diffusion or trait anger. They were significantly different on measures of perfectionism and trait anxiety.