We have studied the hydrogen absorption kinetics of Zircaloy-4 massive samples at 623 K and at an initial hydrogen gas pressure of 30 bar, using the volumetric technique. The specimens were Ar etched and Au Pd covered (50 nm thick) prior to measurement in order to obtain uniform hydride fronts during hydriding. The resulting hydride phase has a face center tetragonal lattice (a = 0.497 nm, c = 0.485 nm; ε phase) and composition ZrH y with y = 2.0 +/- 0.1. During the absorption process three successive kinetic stages could be identified before saturation: (i) an initial stage with low and constant hydrogen uptake rate, limited by diffusion through an oxygen-rich region in the Au Pd/Zry-4 interface, (ii) an stage where the hydride fraction grows as t 5 / 2 , and (iii) a final stationary state with constant hydrogen absorption rate where the hydride front advances at 26 μm min - 1 . We have discussed the relationship between these stages and the diffusion processes (intra and inter-granular), the nucleation and growth of hydride platelets, and the process of crack formation.