Any of the Primitive Adûnaic consonants could appear medially between vowels, with the exception of [ŋ], which only appeared before another velar (SD/432). Primitive Adûnaic could have pairs of consonants medially as well, with almost any combination allowed (SD/418). The most notable exception is [n], which could not appear before consonants from different series, with the exception of the combinations [nw] and [nj] (SD/420, 432). This is because [n] assimilated in position to following consonants (SD/420).

Although most combinations were allowed, pairs of stops were rare. Consonant clusters tended to arise from the combination of the second and third consonants of a triconsonantal-root like KALAB, and such bases tended to have continuants in at least one of those positions (SD/417).

Clusters of three or more consonants did not appear, because words and affixes always began and ended with either a vowel or a single consonant (SD/418). Thus, no combination of word elements could produce a cluster of more than two consonants.