The quantitative photochemistry of the platinum organometallic complex, Cp'Pt(CH3)(3)(CP' = eta(5)-C5H4CH3), has been investigated in methylcyclohexane and n-pentane solutions at 293 K following UV irradiation into the lowest lying absorption bands. Absolute photochemical quantum efficiency (phi(cr)) results obtained for Cp'Pt(CH3)(3) at 313 and 366 nm reveal that the system very effectively photoreacts with phi(cr) = 0.34-0.41 in these solvents and 0.79-0.85 when 53 mM Et3SiH is incorporated. These photoefficiencies indicate that the quantitative photochemistry is 2 orders of magnitude higher than previously recognized. The application of Cp'Pt(CH3)(3) as an effective photoinitiator for hydrosilylation reactions involving vinyl/hydride silicone mixtures is demonstrated.