The parallel implementation of unstructured adaptive tetrahedral meshes for the solution of transient flows requires many complex stages of communication. This is due to the irregular data sets and their dynamically changing distribution. This paper describes the use of Shared Abstract Data Types (SADTs) in the restructuring of such a code, called PTETRAD. SADTs are an extension of an ADT with the notion of concurrent access. The potential for increased performance and simplicity of code is demonstrated, while maintaining software portability. It is shown how SADTs can raise the programmer’s level of abstraction away from the details of how data sharing is supported. Performance results are provided for the SGI Origin2000 and the Cray T3E machines.