This report contains analyses (including for the first time, specific gravity) and source data for 310 natural gas samples from wells and pipelines in 16 states. All samples were obtained and analyzed in calendar year 1978 as part of Bureau of Mines investigations of the occurrences of helium in natural gas begun in 1917. In late 1965 foreign gasfields were included. The analyses are made by mass spectrometer and a special helium analysis apparatus, as described in Bureau of Mines bulletins 486 and 576. Bulletins 486, 576, and 617 contain analyses and source data for 5,218 samples collected from 1917 through 1960. Seventeen other information circulars reported on 6,355 samples from 1960 through 1977. In 1976 a compilation of 10,562 analyses of samples from oil and gas wells and gas pipelines in 37 states and 23 foreign countries made prior to 1975 was published by the National Technical Information Service (Springfield, Virginia 22161) of the U.S. Department of Commerce. The title of the compilation is "Analyses of Natural Gases, 1917-74." The catalog number of the publication is PB 251- 202. NTIS also distributes the information on a magnetic tape file under catalog number Bureau of Mines tape PB 283-264.