HREELS and XPS indicate negligible dissociation of ClC3H6I during adsorption at 100 K. During TPD, no ClC3H6I desorbs for coverages below 0.4 ML. For higher, but not multilayer coverages, parent ClC3H6I desorption occurs in two peaks, 200 and 230 K. After even larger doses, unsaturable multilayer desorption occurs at 170 K. HREELS indicates that most C-I bonds dissociate by 205 K. The following reaction paths are proposed on the basis of TPD and HREELS results. When the C-I bond breaks, 3-chloropropyl fragments, C(a)H2CH2CH2Cl, are formed and these either lose HCl to form eta(3)- or eta(1)-allyl or lose a beta-hydrogen to form 3-chloro-di-sigma-propylene. Some eta(3)-allyl groups hydrogenate to either propylene, some of which desorbs at 240 K, or n-propyl, some of which hydrogenates to release propane at 250 K. Other eta(3)-allyl groups isomerize to eta(1)-allyl. At 250 K, 3-chloro-di-sigma-propylene eliminates chlorine as HCl and also releases H atoms that hydrogenate neighboring C-3 fragments. The eta(1)-allyl fragment either hydrogenates and desorbs as propylene at 325 K or isomerizes to propylidyne. Propyl and di-sigma-propylene moieties rearrange to form propylidyne or release propylene at 325 K. Interestingly, there is some benzene desorbing at 375 K. To account for it, a diene metallacycle is suggested. Atomic iodine desorbs at 825 K. Comparisons of the thermal chemistry of ClC3H6I on Ag(111) and Ni(100) are made as are comparisons of ClC3H6I with other C-3 adsorbates on Pt(111).