DURING experiments aimed at the microbiological side-chain degradation of cholesterol and cholestenone, reaction products were sometimes observed, which apparently were formed under the influence of sunlight in methylene chloride (Fig. 1). This solvent was used for extraction of the culture media. Like other halogenated hydrocarbons it is frequently utilized in microbiological preparation of steroids¹ and in their biochemical, spectro-scopical and clinical analysis. The transformations described here may therefore be of general interest.