The 213.9 nm gas phase photolysis of phenylcyclopropane yields cis-1-phenylpropene, trans-1-phenylpropene and 3-phenylpropene as the principal products. The formation of these products is efficiently quenched by either neopentane or tetramethylsilane. Xenon is an inefficient quencher. The total product quantum yield as pressure tends to zero is found to be 0.25 ± 0.05. Since fluorescence is not observed, 75% of the absorbed photons are unaccounted for. The results of this study are discussed in terms of photochemical and photophysical mechanisms for aromatic hydrocarbons.