Maa (Maasai) has at least 24 different nominalizers. Of these, earlier works have called -et an Instrumental and a-...-ani an Agent nominalizer. However, some derivations show that these labels do not cover all relevant nominalizations, and others raise the specter that there could be some overlap in semantic role meaning. Hence, this paper explores the synchronic semantics related to the opposition between -et and a-...-ani formations. Using a sample of 137 nominalizations taken from a much larger database, the authors investigate whether there is overlap in inherent aspect of the verb stems these two nominalizers occur with, semantic role of the verb to which the resulting nominalization refers, and animacy or humanness of the resulting referent. The study shows that a proto-type notion of animacy better predicts choice between -et and a-...-ani than does semantic role. Insofar as these two forms are concerned, the authors conclude that a-...-ani would best be termed an Animate nominalizer, but continue to call -et an Instrumental nominalizer until further contrastive study of the remaining nominalizers is undertaken.