Transitivity helps explain the distinction between the Niphal and Hitpael stems in Biblical Hebrew. Biblical Hebrew demonstrates a large area of overlap between these two stems. Moreover, some verbal roots prefer one stem over the other, while allowing some exceptions. For example, HPK "turn" appears 34 times in the Niphal, but only four times in the Hitpael. In contrast, KSH "cover" appears nine times in the Hitpael, but only twice in the Niphal. Scholars' definitions of these two stems do not adequately explain these preferences. I propose that transitivity allows us to understand the distribution of some roots between these two stems. Linguists have shown that voice relates to transitivity. Transitivity is a complex category, as Hopper and Thompson (1980) show, designating more features than the number of participants, especially the level of affectedness of the Patient, aspect (telicity), and individuation of the the Patient. Furthermore, Bakker (1994) demonstrates a complex relationship of the Ancient Greek middle voice to the transitivity of event type, and Kemmer (1993) claims that the middle voice across languages can be defined, at least in part, by the distinction between participants. Since Hebraists agree that the Niphal and Hitpael express voice alternations, including passive and middle voice, I will analyse the Niphal and Hitpael according to modern linguistic models of voice (namely, passive and middle voice) and the relationship of voice to transitivity. Once I demonstrate the transitivity traits of the Niphal and Hitpael, I will explain how transitivity explains the tendencies of some roots to appear in one root over the other. Furthermore, I will show how authors may express an atypical level of transitivity with a rarer stem for a given verb, which could explain rare occurrences of a root in a particular stem.