This study was aimed at investigating the semantic integration ability of people with WS in building up a coherent and gist theme from the context of presented sentences. Previous studies have indicated rich lexical semantic knowledge and typical semantic priming in this clinical group, but atypical brainwave patterns have been reported in studies of semantic comprehension. An integration difficulty hypothesis of merging meanings into sentences was proposed to explain the discrepancy (Tyler et al., 1997). In this study, this hypothesis was examined by means of proposition integration. Participants were presented sentences embedded with different numbers of propositions under various scenarios. Successful integration of semantically related propositions under same scenario was demonstrated by high false alarm recognition to sentences with more propositions (a maximum of four in this study). The results revealed that healthy adults showed integration ability when the number of propositions in a sentence were more than three, with increased false alarm rates and confidence ratings, whereas people with WS showed no differences in sentences with increased proposition numbers. Typically developing children controls confined recognition phenomenon to sentences carrying more than two propositions. Hence, it was concluded that contextual effects in terms of proposition integration was a gradual development from childhood into adulthood and a deviant development in people with WS. (Contains 2 figures and 2 tables.)