The excess demand for housing assistance in the United States is well documented, but little is known about the factors that contribute to a family's likeliness to receive housing assistance. This study tracks 3,237 low-income families in 20 large US cities over a 9-year study period to see which families would wind up receiving housing assistance. Thirty percent of the families subsequently received either public housing or voucher-based assistance. Families experiencing greater socioeconomic disadvantage and episodes of homelessness were more likely to receive housing assistance. Neighborhood characteristics were weakly associated with the receipt of housing, and health and criminal justice measures showed no associations with the likelihood of receiving housing assistance. Our findings show that housing assistance is a scarce resource that only reaches a minority of those who are eligible, but that the minority who do receive assistance is disproportionately composed of the most economically disadvantaged families.