The authors have been studying the addition of ozone to terpenes and the oxidation products of terpenes with ozone. In this report, β-isopropenyl-δ-acetyl-n-valeric acid and aldehyde were obtained by the oxidative decomposition of limonene monozonide with chromic oxide. A small quantity of hexahydro-p-acetyltoluene was also obtained by hydrogenation of the neutral part. It was first presumed that the main component of limonene monozonide was limonene-1, 2-monozonide, but a small quantity of limonene-8, 9-monozonide was also produced when limonene was ozonized in glacial acetic acid.