The products (predominantly unsaturated aldehydes) from photolysis in methanol of a series of 6,6-dimethylbicyclo[3.1.1]heptan-2-ones are reported. These results are rationalized on the basis of stereochemical interactions and the apparent preference for cleavage to occur adjacent to the less highly substituted α-carbon but more stable alkyl radical. It is concluded that the photochemical behavior of α-cyclobutyl ketones displays a closer parallel to the α-cyclopropyl ketones than previously recognized and that cleavage will occur preferentially on the side of the carbonyl group remote from the four-membered ring whenever possible. The synthetic steps involved in the preparation of the ketones from 'pinene' precursors are described.