[en] Using the techniques of pulse-radiolysis and of the absorption of Lyman-α radiation by hydrogen atoms, the absolute rate constants of reaction of hydrogen atoms with several olefins have been measured at room temperature. The rate constants (k/10^-12 cm³ molecule^-1s^-1) are as follows: Ethylene 1.1+-0.1, Propylene 1.7+-0.1, 1-Butene 2.0+-0.5, trans-2-Butene 1.1+-0.2, cis-2-Butene 1.0+-0.1, 2-Methyl-1-propene 5.2+-0.6, 2-Methyl-2-butene 2.4+-0.3. These rate constants were invariant over hydrogen pressures ranging from 200 to 1200 Torr. (author)