Abstract: The Interface Hypothesis has made specific predictions about L2 acquisition and such predictions can be extended to L3ers because of interface delay interpretations.The paper examines the acquisition of three English syntax-discourse interface constructions (Topicalization, Focus Fronting and Left Dislocation) through (bilinguals learning English as L3) evaluating the acceptability of embedded test sentences with and without pronouns in the context on a scale to test IH.Our data provide evidence against three current L3 acquisition models — L1 factor, L2 factor and CEM and argue for both cumulative enhancement and inhibition to possibly occur in the process of L3 acquisition.