A computer programme for the calculation of radioactivity data from liquid-scintillation counters fitted with external standards.

1. A method for transferring data from liquid-scintillation counters to automatic punched-card read-out is described. 2. A method of calibration of an external standard is presented that supplies sufficient information for the correction of quenched data by computer. 3. A computer programme in FORTRAN IV is described that calculates the data from one isotope, or two isotopes counted simultaneously, and that incorporates features for examining the reproducibility of the input data. 4. With the methods described, quench correction of samples containing either (3)H or (14)C was accurate until samples were quenched 70%. When the two isotopes were both present in one sample and counted simultaneously, the correction was accurate until the samples were quenched 60%. When quenching was greater than either 70 or 60% respectively, its correction was still possible but with slightly diminished accuracy and with greater variability.