One of the important quality indices of petroleum products is the content of unsaturated compounds, which is determined by means of an iodometric or bromide-bromate method and is expressed as an iodine number or bromine number. These methods are time- and labor-consuming and in many instances are inadequate in sensitivity. This paper describes a new method of analysis based on the equimolecular reaction of ozone with the unsaturated components of the test product. In determining the content of unsaturated hydrocarbons, and ADS-3 double-bond analyzer as used. In order to determine the feasibility of using this method in the analysis of petroleum cuts such as naphthas, jet fuels, kerosines, etc. , the authors made up an artificial mixture consisting of C//5-C//7 alkenes, alkanes, and isoalkanes, the idividual composition of which was checked by a chromatographic method. Results show that the ozone method is sensitive down to 10** minus **1**0 mole/ml, and the reproducibility is 2%; the probable relative error of the method is 1. 5%; the time required for analysis is 10 min.