The introduction of the notion of pseudo-pres-sures allows rigorous, analytical solutions to a wide range of gas flow problems. However, in order to apply pseudo-pressuro based solution techniques a num-ber of cumbersome procedures are invoked to take res-ervoir pressures and convert them into pseudo-pres-sures. These include dimensionless table look up, numerical integration and regression analysis. To then convert the corresponding pseudo-pressures back to their analagous reservoir pressures, graphical and/or regression techniques need to be employed. This paper, then, examines the use of a semi-analvtical approach to real gas pseudo-pressure/pres-sure conversion calculations and its application to well test analvsis. The semi-analytical approach to real gas pseudo-preseures allows, a simple, direct and exact solution for converting pseudo-pressure to pressures and vice Versa. No numerical integration, graphical or regression techniques are needed and the approach is well-suited for desktop or minicomputers. It is applicable to a Wide range of reservoir properties ties including sweet and sour gases, reservoir pres-sures up to 10,000 psia and reservoir temperatures up to 460'F.Well test ana]vees have then been carried out on a number of published buildup, drawdoun and deliver-ability tests using the semi-analytical approach. 227 Comparisons have been made between test interpreta-tion results using traditional pseudo-pressure calcu-lations and analyses from the semi-analytical ap-proach.