This method describes a procedure for determining paraffin, olefin, naphthene and aromatic hydrocarbon types in stabilized gasolines or fractions therefrom. The endpoint of these stocks (ASTM D 86) should not exceed 196°C (385°F), see NOTE 1. Paraffins and naphthenes are determined by carbon number with cyclopentane, methylcyclopentane and cyclohexane determined individually. C6 minus hydrocarbons can be reported either individually or by carbon number. Aromatics are determined by carbon number through C8 with the C9+ determined as a composite. Olefins are reported undistributed.