This article reports the findings of a National Institute of Mental Health (NIMH) services demonstration project that used a mobile case management team to serve homeless mentally ill clients. The project examined three issues: (1) factors associated with client engagement in case management, (2) clients' perceptions of how case management affected their quality of life, and (3) significant differences between clients who remained engaged in case management services and those who discontinued involvement. The results indicated that clients who received more frequent case management contact, had higher assessed independent living skills, were older, were less likely to be substance abusers, and had experienced fewer periods of homelessness and fewer prior psychiatric hospitalizations were more likely to remain engaged in case management services. After six months of case management, clients perceived significant improvement in their global well-being, living situation, use of leisure time, finances, and physical health. Implications for providing case management services to homeless mentally ill people are presented.