The research defined boarder babies as infants under age 12 months who remain in the hospital beyond the date of medical discharge, and abandoned infants under age 12 months who are unlikely to leave the hospital in the custody of their biological parents once they are discharged. The analysis revealed that at some time during calendar year 1991, a total of 10,000 boarder babies resided in 573 hospitals in 101 counties. Boarder babies had a median length of stay of 5 days after medical discharge up until the census day. Twenty-one percent stayed from 21 to over 100 days. The average cost of care was estimated at $2,930 for 5 days, the median length of stay past medical discharge, and $12,892 for 22 days, the average length of stay. At some time during 1991 the country had at least 12,000 abandoned infants. More than three-fourths of the boarder babies and abandoned infants who were tested had been exposed to drugs. Eight percent of all drug-exposed infants were known to be HIV-positive, but 68 percent of drug-exposed infants were either not tested or had an unknown HIV status. Slightly over 60 percent of the boarder babies were expected to leave the hospital with their biological parents. Tables and footnotes