Under normal gravitational conditions the measurement of the thermal conductivity lambda is often strongly influenced by thermal convection. Heat transfer by convection superposes the heal transfer due to thermal conduction. Systems in which the gravity effects are compensated, e.g. under microgravity conditions, offer decisive advantages because natural convection is strongly suppressed. In this paper an apparatus is described enabling accurate measurements in fluids with low viscosity without any gravitational influence. Comparative measurements carried out in the ’Drop Tower Bremen’ using isopropanol, ethanol and cyclohexane are presented and compared to data available in the literature.