The rate constants for H atom reactions with Cl-2 and F-2 have been measured by monitoring the loss rate of hydrogen atoms in the presence of excess [Cl-2] and [F-2] via time-resolved, laser-induced Lyman-alpha fluorescence. The rate constants for H + F-2 and H + Cl-2 were found to be 2.4 +/- 0.4 (26) x 10(-12) and 2.52 +/- 0.18 (2sigma) x 10(-11) cm(3) s(-1), respectively. The result for H + F-2 is consistent with the recommendation of Baulch et al. [J. Phys. Chem. Ref. Data 1981, 10 (Suppl. 1)], and our k(H + Cl-2) value is consistent with the majority of previous measurements.