Absolute second-order rate coefficients for the reaction of W-n,, with cyclopropane have been measured using a large-bore flow tube reactor coupled with a laser ablation metal cluster source and a laser ionization/time-of-flight mass spectrometric detector. Rate coefficients for the depletion of W clusters by cyclopropane in He carrier gas show no helium bath gas pressure dependence between 0.5 and 2.0 Torr but decrease with increasing temperature between 277 and 351 K, Reaction rates are significantly higher than those predicted by a simple hard-sphere collision model. A polarizability-based model has been successfully employed to explain the reactivity observed. The model implicates van der Waals complexes as precursors to chemisorption of cyclopropane by W,,.