The kinetics of the aqueous-phase, stereoretentive hydrogenation of alanine to alaninol over 5 wt % Ru/C catalyst in a three-phase stirred batch reactor is presented. Alanine readily undergoes hydrogenation when in the carboxylic acid form (-COOH), a condition that can be achieved by acidifying the reaction solution with phosphoric acid. The conversion rate is not limited by mass-transport resistances over the ranges of temperature (353-398 K), hydrogen pressure (1.7-13.8 MPa), alanine feed concentration (0.22-0.46 M), and phosphoric acid concentration (0-1.2M) investigated. A Langmuir-Hinshelwood (L-H) kinetic model is presented in which protonated alanine and undissociated phosphoric acid compete for one set of surface sites and H-2 dissociatively adsorbs on a second type of site. The average error between the experimental and predicted conversions over all data collected was 8%.