Until the beginning of the 1990s, the gas distribution pipelines in Latvian and all Baltics were built and operated in accordance with the technical standards of the former USSR, using the materials, techniques, technology and control methods of that particular period and technological framework. It was assumed that the service life of the underground steel gas pipelines is 40 years, which has already been exceeded for significant portion of such pipelines and will only increase in the following years. Therefore, it is necessary to assess the technical condition of these pipelines and make operational decisions to strengthen their monitoring or stop the operation of particularly dangerous sections. The research deals with a methodological basis for determination of technical condition of steel underground distribution gas pipeline in a context of ongoing gas supply diversification. It is based on and performed in accordance to technical condition assessment data available for steel underground distribution gas pipelines and the accumulated experience of engineering practice.