Both the 2-L counter, described in GSC I (Radiocarbon, 1962, v. 4, p. 13–26), and the 5-L counter (GSC IV, Radiocarbon, 1965, v. 7, p. 24–46) were operated routinely during the past year. Approximately half the determinations reported were obtained from each counter. The 2-L counter was operated at 2 atm except for August and September, 1968, when it was operated for the first time at 1 atm. This allowed for the counting of most small samples without the necessity of mixing with dead gas. The 5-L counter was operated at 1 atm, except for the same period when it was operated at 4 atm. Carbon dioxide is used as the counting gas, and both counters are of the proportional type.