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The kinetics of the photochemically initiated reactions between some alkyl halides (chlorides, bromides, and iodides) and some triorganotin hydrides have been examined in cyclohexane at 25C. Chains are generally terminated by bimolecular radical-radical reactions. In general, with alkyl chlorides, the rate-controlling step for chain propagation involves chlorine abstraction by a triorganotin radical, while with bromides and methyl iodide, the rate-controlling step involves hydrogen abstraction from the hydride by the alkyl radicals. Absolute rate constants have been determined by the rotating-sector technique. Chain termination rate constants are near the diffusion-controlled limit for the self-reactions of both alkyl radicals and triorganotin radicals. The evaluation of the rate constants for both propagation reactions and for two out of the three possible termination reactions means that these processes are now among the best understood two-step chain reactions. (Author)