This work shows the results of a systematic study of transient pressure analysis of gas flow under either constant bottom-hole pressure conditions or the constant wellhead ‘Pressure conditions. The effects of formation damage, wellbore storage and highvelocity ‘flow are included in the model. The analysis of simulated well tests showed that the interpretation methods used for liquid flow are generally accurate when the m(p) is used. For these conditions, a graph of 1/qD vs log tD presents gradually lower values than the exact conventional value of liquid flow of 1.1513 as the value of pwf decreases; for pressure buildup conditions a graph of mD(1,ΔtaD)/qD(ΔtaD=0) vs (taD+ΔtaD)/ΔtaD shows values of this siope witnin 1% of tfte 1.1513 vaTue. The maximum error was in the rate performance simulated cases that included high-velocity flow, being less than 13%. This upper limit occurs when the formation has a relatively "high" permeability (around lmd) and the rate performance test is affected by high-velocity flow. It was found that pressure buildup tests are superior to rate performance tests because high-velocity flow does not affect the slope of the straight line portion of the buildup curve.