Abstract
The signs of the Leslie viscosities α2 and α3 for nematics consisting of disk like molecules are discussed. It is predicted on theoretical grounds that for disk like molecules α3 is always positive while α2 should be able to exhibit both positive and negative values. This is the first time that the possibility of a positive α2 is discussed in the literature. Provided that the prediction is correct, the nature of the flow behavior of disk like molecules is discussed.