Matrix isolation studies combined with infrared spectroscopy of the twin jet codeposition of ozone and cis-2-butene into argon matrices have led to the first observation of several early intermediates in this ozonolysis reaction. Specifically, evidence is presented for the formation and identification of the long sought-after Criegee intermediate, as well its confirming evidence for earlier reports of the primary and secondary ozonides. These species were observed after initial twin jet deposition, and grew upon annealing to 35 K. Extensive isotopic labeling (O-18 and O-16,O-18 mixtures) experiments provided important supporting data. Detailed theoretical calculations at the B3LYP/6-311++G(d,2p) level were carried out as well to augment the experimental work. Merged jet (flow reactor) experiments followed by cryogenic trapping in solid argon led to the formation of "late", stable oxidation products. Photochemical reactions of ozone with cis-2-butene Was Studied as well, as was the photochemical behavior of the primary and secondary ozonides.