The ozonide cis-trans ratios, for both normal and cross-ozonides, have been examined, in a number of cases, in pentane and in benzene solutions. In benzene, at 25 "C, almost invariant cis-trails ratios are observed, regardless of the geometry and initial concentration of olefin. In pentane, these ratios have been found to depend, both at -78 and 25 "C, on the geometry and the initial concentration of the olefin when 1,2-disubstituted ethylenes with bulky substituents are ozonized. However, the crossozonide cis-trmu ratios obtained from trisubstituted ethylenes do not depend on the initial olefin concentration. A tentative mechanistic proposal is suggested in terms of transitory zwitterion-oletin adducts.