This study examined incarceration histories and shelter use patterns of 7,022 persons staying in public shelters in New York City. Through matching administrative shelter records with data on releases from New York State prisons and New York City jails, 23.1% of a point-prevalent shelter population was identified as having had an incarceration within the previous 2-year period. Persons entering shelter following a jail episode (17.0%) exhibited different shelter stay patterns than did those having exited a prison episode (7.7%), leading to the conclusion that different dynamics predominate and that different interventions are called for in preventing homelessness among persons released from jail and from prison. (Contains 4 tables and 3 notes.)