Criminal and aggressive behaviors are frequently observed among those recovering from substance abuse problems. In the present one-year longitudinal study, a national sample of residents from self-governed, communal living recovery homes for substance abuse completed baseline and follow-up measures of criminal and aggressive behavior. Results indicated that a length of stay of six months or longer was associated with lower levels of self-reported criminal and aggressive behaviors at the one-year follow-up. Environmental mechanisms proposed as influences for these outcomes, as well as treatment implications, are discussed.