The Medwise computer program for medical diagnosis was previously evaluated when the knowledge base (KB) contained 2400 disease profiles. Using 104 actual patient cases, the program then established the correct diagnosis in 93% of the cases. Since that time, the KB has been expanded and now contains 3600 disease profiles. The authors are interested in learning whether the expanded KB effects the performance by analyzing the same set of patients under the new conditions of an enlarged KB. To this end, they ran exactly the same input files as used in the previous evaluation. The results document that the performance is virtually invariant for the extent of the KB employed. It is emphasized that Medwise employs a special technique to assist the interpretation of medical information, namely a matrix representation of medical knowledge.