This paper describes a study on the reaction kinetics of an ethylene tetramerisation catalyst comprising Cr(acac)(3), a bis(diphenylphosphino)isopropylamine ligand and MAO as catalyst activator. The reaction rate was found to be dependent on temperature as well as on ethylene concentration to the order of 1.57. The catalyst deactivation rate was found to be a function of temperature. A reaction rate model was developed providing good description of reaction performance in the temperature range of 35-45 degrees C and pressure range of 30-45 bar. Selectivity data is provided which illustrates the effects of pressure, temperature and time on stream. Increased temperature and decreased pressure result in increased 1-hexene and decreased 1-octene selectivity, while time on stream data indicates the occurrence of secondary incorporation reactions of I-hexene and 1-octene. (c) 2006 Elsevier B.V. All rights reserved.