The different inflow performance relationships (IPRs) that have been proposed in geothermal and petroleum reservoir engineering are reviewed. The applicability of these relationships to well production tests is analyzed, and the geothermal IPRs for pure water, for the binary H(2)O-CO(2) and ternary H(2)O-CO(2)-NaCl mixtures (with different salinities) are presented. The method to determine the maximum flow rate for a well is described. Two representative IPRs for petroleum systems and two for geothermal systems that consider the fluid as a ternary mixture H(2)O-CO(2)-NaCl (for salinities less than 5%, and between 5% and 20%) are compared. It is concluded that IPRs may be used to determine the maximum flowrate of a well at any time during its productive life. (c) 2008 Elsevier Ltd. All rights reserved.