Among the Tibeto-Burman languages the importance of the marking of transitivity varies greatly, from transitivity not being a very useful concept at all to being extremely important to the understanding of the morphology of the language. In this paper an example of the latter type is discussed, the Rawang language of northern Myanmar (Burma). In this language all verbs are clearly distinguished (even in citation) in terms of transitivity by their morphology, and there are a number of different affixes for increasing or decreasing valency. A very interesting phenomenon related to the importance of transitivity differences that occurs in Rawang is the phenomenon of what I call “transitivity harmony”. All auxiliary verbs in this language are transitive, and when they appear with a transitive main verb, they simply follow that verb and the two verbs together take one set of transitive-marking morphology. If instead the main verb is intransitive, then the auxiliary verb must be made intransitive by the reflexive/middle voice suffix to harmonize with the intransitive verb. This pattern holds even when the main verb is overtly nominalized. Aside from establishing transitivity harmony as a typological phenomenon, this paper will also discuss some of the motivations for such a pattern of marking and its significance for understanding event profiling.