The kinetics of hydrogenation of the acrylonitrile-polybutadiene (NBR) rubber by the action of hydrazine in the presence of selenium and oxygen was studied by varying reaction parameters such as latex and catalyst concentrations. The method of initial rates gives a reaction order of 0.91 and a rate constant of 3.2 x 101 L mol(-1) h(-1) in relation to the NBR latex concentration, and an order of 0.86 and a rate constant of 3.3 x 10(1) L mol(-1) h(-1) in relation to the catalyst concentration. Based on these values, a first-order mechanism with the formation of a diimide intermediate is suggested, which is formed through the oxidation of hydrazine in an oxygen atmosphere in the presence of selenium catalyst. This diimine species reacts rapidly, reducing the carbon-carbon double bonds of NBR resulting in the formation of HNBR rubber. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 3605-3609, 2012