The rotational viscosity coefficients &ggr;1are measured with the rotating field method as a function of temperature in the nematic phases of 4‐methoxybenzylidene‐4′‐n‐butylaniline, 4‐n‐pentyl‐, and 4‐n‐octyl‐4′‐cyanobiphenyl, of the eutectic mixture of two 4‐n‐pentylphenyl 4‐alkoxybenzoates and of the eutectic mixture of the two isomers of 4‐methoxy‐4′‐n‐butylazoxybenzene. Equations are proposed which describe the temperature dependence very well. The Leslie coefficients &agr;iare calculated from the &ggr;1values and recently measured shear viscosity coefficients.