AbstractSpiropentane was photolyzed using xenon 1470Å resonance light source at room temperature. The photolysis products were analyzed by means of FID‐gas‐chromatographic technique. Through the information about the yields of products, the major primary process of this light‐molecule interaction was assigned as C‐C bond breakage. Methylenecyclobutane, which has been an identified isomerization product of excited spiropentane molecule, was not able to be produced at present high excitatio