The primary aim of this report is to introduce how to use the 1220 Quantulus liquid scintillation counting system for the quantitative measurement of extremely low levels of ^14C beta activity. It starts from vials setting, and technique of operation of Queue Manager software for controlling 1220 Quantulus is given. Using teflon/copper vials with Quantulus, very high accuracy is now attainable in this as shown by Gupta and Polach(1985).