This is a method for determining most of the components, including low concentrations of total C6 + hydrocarbons, normally found in a wide variety of gaseous hydrocarbon mixtures obtained from refining processes or from natural sources. It may be used as an alternate to UOP Method 539 except when the distribution of ethylene, ethane and carbon dioxide is required. Butene-1 is not resolved from isobutylene by either method and argon is determined as a composite with oxygen. The instrumentation is less elaborate than that described in UOP Method 539 and requires only slight modifications to a standard chromatograph. The lower limit of detection for a single component is 0.1 mol-%.