This study examined the factor structure of symbiosis between individuals and organizations (SIO) scale using a sample of full-time workers with and without off-the-job activities such as volunteer work. The effects of SIO relating to self-development as a result of these off-the-job activities and work commitment were also examined. 413 respondents were used in the factor analysis of SIO items. Using a sample of 236 workers with off-the-job activities,a model regarding the interrelationships among the four commitment forms and self-development was assessed by using path analysis applying structural equation modeling. The findings revealed that SIO was constructed of three factors,(a) mutual respect,(b) dependence on organizations,and (c) respect for rights and that SIO was associated with self-development and work commitment via job involvement. The results suggested that SIO facilitated both on and off-the-job activities.