OPC UA is the evolution of the well known OPC COM and XML specifications. OPC UA adopts a very complexsoftware infrastructure to realise the communication among industrial applications; furthermore it featuresmany mechanisms realising data exchanges, whose tuning depends on several parameters. The aim of thispaper is to deal with the performance evaluation of OPC UA. The main data exchange mechanisms which mayinfluence performance of the client/server communications will be pointed out; then, the analysis of the overheadthey introduce will be presented and discussed. Finally, some guidelines about the setting of OPC UA mechanismswill be given on the basis of the results achieved.