The presence of an agent in the interpretation of 'astem'rnforms and its absence 1n the basic stems define thernfunction of 'a-' as agentive or causative aff~x in Amharic.rnThe formal analysis is also plain that 'a-' atcaches to nonagentivernbasic stems. The common interpretation of 'as-stem'rnforms show double (that is, ultimate and immediate) agency inrnrelation to the resulting event whether the stems have agentrnor not in their argument structure. This phenomenon has beenrnfrequently stated in the literature as indirect causativern(Bender and Hailu, 1978), (Appleyard,1972) causative of thernpassive (Leslau, 1967) and factitive (Bender and Hailu, 1978)rnfunction of the affix 'as-' .rnThis paper verifies the observed passive representationrnof the base of 'as-stem' causatives in terms of ProminencernTheory of Argument Structure (Grimshaw, 1990). According tornthis theory, an external argument cannot be introduced to anrna-structure in which there is one. Hence, passivization ofrnagenti ve verbs is necessary in order to suppress the agentrn(external argument), that is, to give way for the integrationrnof arguments in causativization . Accordingly, the so - calledrn'as-stem' causatives have been derivationally related to thernbasic stems by analysing the causative form into 'a-s-stem',rnrepresenting passivization and causativization as separaternaffixational processes.rnBy providing morphophonological explanations that relatern[sl to the passive morpheme /t-/ this approach offers arnunified account of causativization in Amharic .