Based on the thermodynamic properties of HCFC123 obtained by using a modified Benedict-Webb-Rubin (MBWR) equation of state fit to experimental measurements, the theoretical performance of HCFC123 has been assessed as an alternative to CFC11 by using standard refrigeration parameters, including pressure ratio, specific compressor displacement, coefficient of performance, and shaft power. This study indicates that a CFC11 compressor working with HCFC123 will have lower adiabatic head rise, efficiency and volume flow. This performance difference should not exclude HCFC123 as an alternative to CFC11 since most of the existing machines are oversized for a particular application and thus performance attained with HCFC123 could be adequate.