The Unified Medical Language System integrates about 800,000 concepts from 99 biomedical terminologies. Each concept is assigned to at least one semantic type of the Semantic Network. During the integration, it is unavoidable that some classification errors and inconsistencies will be introduced. In this paper, we present an auditing technique to find such errors and inconsistencies. Our technique is based on an expert reviewing the pure intersections of meta-semantic types of the metaschema, a compact abstract view of the Semantic Network. Results regarding the pure intersections are reported. The analysis results for pure intersections with 1 to 6 concepts are presented. Various kinds of errors are identified.