This study sought to ascertain the presence of meaningful subtypes of alcohol and other drug involvement among homeless persons. Subtypes were derived using factor analysis to determine dimensions underlying alcohol involvement and cluster analysis to create unique subtypes. The types with the highest level of alcohol or drug use had the longest period of continuous homelessness and were less likely to have exited from homelessness when reinterviewed 6 months later. The dimensions represent a more sophisticated framework for describing alcohol and drug involvement among homeless persons and may be useful for practitioners in conducting assessments, designing programs, and planning interventions.