In this paper, a frame-based description of verbal polysemy is used to answer some questions concerning syntactic behavior and argument structures associated with complex predicates in Persian. In Persian a number of CPs consisting of a light verb (LV) and a preverb (PV) participate in causative alternation. The causative variant is formed with the LV ændaxtæn 'cause to fall' and the anti-causative variant is formed with oftadæn 'fall'. In some contexts these verbs do not participate in causative alternatioin. In other words they do not have an anti-causative variant in such contexts. The peculiar behavior of these verbs in different contexts is explained in the framework of Frame Semantics [2]. I will argue that these verbs are associated with two semantic frames and just one of them is compatible with both causative and antiicausative form. The other frame is compatible with causative form but incompatibel with anticausative form hence no anticausative variant. As for the A-structure of CPs, using the notion of Frames [5] it is proposed that the whole construction including the CP determines its A-structure. It is not detrmined just by PV [9] or compositionally by PV and LV [6].