Large alkyl radicals and their unimolecular decomposition products are generated and detected by molecular beam photodissociation-photoionization mass spectrometry. Alkyl radicals are prepared by photodissociation of the corresponding haloalkanes in the core of a free jet expansion. Collisional cooling in the expansion stabilizes the primary products and minimizes secondary reactions. The photolysis products are detected by photoionization with coherent vacuum ultraviolet radiation. This technique permits large (greater than or equal to C-6) n-alkyl radicals and their subsequent low-energy decomposition reactions to be studied. The n-heptyl and 5-methyl-1-hexyl radicals are found to decompose by both C-C and C-H bond dissociation pathways. Direct beta(C-C) bond dissociation is only a minor process, indicating that radical isomerization precedes C-C and perhaps C-H bond dissociation.