The Year 2000 (Y2K) problem is a global problem. It is a problem that has impacted almost every industry in the United States and many other countries. It is a problem that has been there for almost half a century but has received global attention only in the past two to three years. It is a problem that has to be fixed before we move into the next millennium. Every computer chip and computer software that uses a two-digit year-field has to be evaluated, replaced or remedied to meet the requirement for a four-digit year-field. Although such a fix may sound simple, in practice it is a massive task to identify, remedy and test all the affected components. Testing is one of the major components in any Y2K project. The work in this thesis concentrates on testing the source code of a major hospital application. The application deals directly with patient-care and thus it is critical to ascertain that the code has been remedied and is practically "error free". A combination of data flow testing and program instrumentation is used to test the programs for this application.