The systematic analysis of protein-protein interactions is a fundamental step for understanding of cellular organiza- tion, processes and functions. Recent high-throughput ex- periments have produced an enormous amount of protein- protein interaction data. However, the analysis of protein- protein interactions has a limitation in effectiveness be- cause of the unreliability of the interaction data. In this paper, we apply semantic similarity measures to quantifying the reliability of protein-protein interactions. We also pro- pose a novel metric, which is called semantic interactivity, to measure the interaction reliability by the integration of Gene Ontology annotations. We evaluate the measurements by comparing the interaction reliability between proteins to their functional co-occurrence. The results show that the in- teraction reliability measured by semantic interactivity has a positive correlation with the functional association be- tween the interacting proteins. Finally, we demonstrate that the semantic interactivity measure can accurately detect po- tential false positive interactions.