Well testing is sometimes reduced to perforating the well in underbalanced conditions, capturing the pressure data and then analyzing it. The primary objective of a Perforation Inflow Test Analysis (PITA) is to estimate the initial reservoir pressure, permeability and skin for evaluating a future development strategy. However, special analytical procedures are required for analyzing the data. In this study, a systematic analytical procedure for estimating meaningful reservoir parameters from perforation inflow tests will be presented. Two major aspects of data interpretation will be discussed: diagnostic analysis and modelling. A straight-line approach is taken to analyze the early-time and late-time data. A special diagnostic technique is required for detecting and estimating positive or negative skins. A distinctive feature of PITA is that it does not require calculation of the inflow rates. Note that the same approach can be applied in overbalanced situations, when there is fluid efflux, rather than fluid influx. When employing straight-line analysis techniques, acceptable estimates of initial reservoir pressure, permeability and skin are only obtained if the test duration is sufficient to achieve radial flow. This is usually not a problem in high permeability reservoirs. However, in low permeability reservoirs, the test duration required to reach radial flow can be prohibitively long. In these cases, the test is often terminated during the transition from well-bore storage to radial flow. Consequently, acceptable estimates of initial reservoir pressure, permeability and skin can only be obtained by extending the analysis into modelling. A rigorous technique for estimating the radius of investigation during the test will be discussed.