The material and flow properties of magnetic fluids - so called ferrofluids - can be significantly influenced by magnetic fields. Two of the most prominent phenomena are the thermomagnetic convection and the magnetoviscous effect. To date, these magnetic field induced effects have always been studied separately, although they can affect each other under certain conditions. With the help of magnetic fields it is possible to induce a convective heat flow in ferrofluids. In earlier studies it is assumed for that case that the classical material properties are constant. However the magnetoviscous effect describes an increase in viscosity under magnetic influence, which occurs in ferrofluids with a certain contingent of large particles. In this paper, experimental results concerning the influence of the magnetoviscous effect on thermomagnetic convection are shown and discussed. Ferrofluids with and without significant magnetoviscous effect have been investigated. (C) 2012 Elsevier Ltd. All rights reserved.