A study has been made of the kinetic relationships governing the hydroformylation of isobutene in the presence of an etriolphosphite-modified carbonyl-rhodium catalyst. A mathematical model of the kinetics of hydroformylation of isobutene has been obtained, satisfactorily describing the dependence of the rate of the reaction on the concentration of the reactants and the reaction conditions in a wide range of variation. The multiple correlation coefficient R amounts to 0.94. The activation energy of 3-methylbutanal formation E has been calculated at 78 +/- 2 kJ/mole.