[en] A review is presented on the present status of the measurements of electron spin resonance (ESR) spectra of paramagnetic particles in the gaseous phase. The theory of ESR spectrometry is presented as well as its application to the gaseous phase ESR spectra. Measurements of the gaseous phase chemical kinetics of atoms and simple radicals by ESR detection are described in detail. Along with the direct measurements of the ESR spectra in the gaseous phase also the technique based on freezing-out of radicals from the flow of reacting gases is described, as well as methods using the so-called spin-trapoing method, in which the highly reactive primary radicals react to form more stable secondary free radicals. From the analysis of their ESR spectra the nature of the primary radical can usually be determined. (author)