Naturally occurring radiocarbon is registered in a proportional counter filled with pure CO2. The CO2 gas is purified in almost the same manner as has been developed by De Vries and Barendsen. Checking of the gas purity is described. A grid proportional counter with an effective volume of about 2.5 liter has been used with CO2-pressures from 1 to 4 atmospheres. At a pressure of 4 atmospheres the net count from contemporary wood is 58 counts/min above a background of 15 counts/min. Dating may at the present stage be extended to 35 000 years by 24 hours counting with 4 atmospheres CO2. A method for checking the discriminating level of the counting apparatus is described.