This article presents a review of the recent literature describing the use of plant callus for the production of biochemicals, as well as specific examples of work done in our laboratory to analyze the production of ribosome inactivating proteins from Trichosanthes kirilowii callus. The article discusses research advances in the development, characterization, and improvement of plant callus cell lines, including new cell lines and potentially useful products, influence of media composition, and environmental conditions on growth and product distribution, cell line selection strategies, and long-term stability.