This publication contains analyses and related source data for 517 natural gas samples from 25 states and 1 foreign country. Of the total samples, 298 were collected during calender year 1985; the remainder were collected earlier, but releases granting permission to publish were not received before 1985. All samples were obtained and analyzed as part of Bureau of Mines investigations of the occurrences of helium in natural gases of countries with free market economies. This survey has been conducted since 1917. The analyses published herein were made by mass spectrometer and chromatograph.