This paper investigates the relationship between the syntactic configuration of two classes of intransitive verbs of motion (the unaccusative and unergative verbs), on the one hand, and certain semantic properties of the respective predicates, encoded in the event structure and the semantic definition of the superficial subject, on the other hand. Hence, it is assumed that the unaccusativity is syntactically encoded and scmantically determined. It is shown that the semantic class of verbs of motion in not homogeneous and that its variable behavior with respect to different unaccusative diagnostics is due to the alternation of syntactically relevant aspects of meaning. The verbs of motion in Russian and Spanish are argued to fall into variuos subclasses, that arise from the combination of two sets of features: the delimitedness (wich can be semantically or syntactically induced) and animacy (which is especially important for the distribution of the semantic component 'manner of motion').