The transition of oil companies in the ‘90s from an internal service for monitoring the development of oil and gas fields to outsourcing revealed the problem of an objective assessment, necessity and sufficiency of the obtained information on the parameters of productive formations. Known methods of analysis of the results of hydrodynamic well testing are based on subjective criteria, which hinders the development of research methods and technologies. The results of a statistical survey of oil and gas industry professionals in Russia, which showed the need to develop an objective system for assessing the quality of the results of hydrodynamic well testing, are analyzed. The authors consider an approach to the formation of a quality assessment system based on an objective criterion – the error of measuring instruments for the physical quantities of technological parameters, the uncertainty of calculation models for indirect measurements and ambiguity of the results when solving the inverse problems of underground hydrodynamics of productive oil and gas reservoirs.