Data are based entirely on monthly population reports submitted to the Bureau of Correction by each county prison and jail. Specifically, the data treat population trends, the largest county prisons, major types of receptions and releases, statuses on December 31, 1960 to 1977, racial distribution, selected offenses by age, maximum sentence distribution, time served by method, and time served by offense. The average daily population in county prisons increased slightly in 1976 and then dropped to pre-1975 levels during 1977. Sixteen county prisons averaged over 100 prisoners per day in 1976 and 1977; these 16 counties accounted for 77.6 percent of all county prisoners in 1976 and 76.9 percent in 1977. In 1976, the number of court commitments received in county prisons continued to increase with a jump of 1.7 percent over 1975 levels; in 1977, court commitments dropped by 8.6 percent. Unconditional releases have risen in the last 4 years, with increases of 2.5 percent in 1976 and 12.5 percent in 1977. Conditional releases increased 11.7 percent in 1976 and 0.2 percent in 1977. In 1976, detention releases fell 4 percent, and in 1977, the number decreased by 7.8 percent. On December 31, 1976 and 1977, whites accounted for the majority of prisoners for the first time since 1966. The major offenses of 1976 county commitments were motor vehicle code violations (15.8 percent), disorderly conduct (8.2 percent), burglary (10.9 percent), larceny (11.9 percent), drunkenness (6.3 percent), and narcotic drug offenses (7.3 percent); these offenses represented 60.4 percent of all county commitments. Footnotes are provided.