The main motivation of screening for chronic diseases is to diagnose disease early in the expectation that benefit from earlier treatment will be enhanced, resulting in reduced mortality. With advances in diagnostic testing techniques, early diagnosis of cancer such as breast, ovarian, cervical and colorectal cancers has become more feasible. Dr. Lee and her collaborator, Dr. Zelen, have developed stochastic models for selecting examination schedules targeted at earlier diagnosis of chronic diseases. The general aim is to provide guidelines for public health programs in the choice of examination schedules. The main features of such schedules are: the initial age to begin a scheduled examination program, the intervals between subsequent examinations and the number of examinations. The theoretical results have been applied to the problem of breast cancer early detection.