His research interests include data mining, bioinformatics, data warehousing, and text mining. He has completed numerous research projects including the development of a formal methodology to support the discovery of potentially interesting knowledge from large collections of data, development of tools to extract information from text documents, development of computational methods for learning action rules, and the development of a mathematical model for representing sequential data. An ongoing research project is the design and development of computational methods to analyze and detect items of interest in biological sequences. Dr. Johnsten's research has been sponsored by the National Science Foundation, Mitchell Cancer Institute, and GE Healthcare.