The kinetic theory for rigid-rod molecules has been successful in describing a variety of experimental observations. from extremely dilute concentrations to the liquid crystalline limit. The theory is formulated in terms of an orientation distribution function, whose tensorial moments can be related to measurable properties. We introduce here a general relation from which evolution equations for moments of arbitrary order can easily be derived. The relation incorporates the effects of flow, magnetic and electric fields (permanent and induced dipoles), as well as "nematic" interactions necessary to describe liquid crystalline transitions. Relevant features of the equation(s) with regard to possible closure strategies are briefly discussed.