Abstract: The goal of this study was to determine whether factors associated with the successful defense and cost of malpractice cases involving the failure to diagnose breast cancer could be identified in medical and legal records. Secondary goals were to develop a multidisciplinary clinical algorithm utilizing National Comprehensive Cancer Network (NCCN) practice guidelines with practitioner risk management strategies. Physician deviations from these guidelines were tracked to identify high-risk areas in the diagnosis of breast cancer. A multidisciplinary clinical algorithm was introduced and practitioner risk management issues were addressed. In this study specific medical, legal, and cost factors were retrospectively abstracted and analyzed to identify associations between medical and legal factors and medicolegal outcome. ProMutual handled 156 malpractice cases involving breast cancer between January 22, 1986, and November 20, 1997. Of the total, 124 cases involving 212 defendants were closed. The closed cases were analyzed, using multivariable stepwise logistic and linear regression, to identify associations between clinical factors and case outcome. Women's health practitioners (WHPs), including obstetrician-gynecologists (OB-GYNs), family medicine, and internal medicine clinicians, were the largest group of defendants (97). Others included radiologists (43), surgeons (33), and pathologists (3). OB-GYNs accounted for 31% of these defendants, with a cost of more than $16 million. The greatest number of specialists represented in the open cases were radiologists, with 38% of the total. The defense model predicts that the probability of successful defense is lessened with inadequate record keeping, a patient that has metastasis and is alive, and a delay in diagnosis of 12 months or more. The overall indemnity model predicts a higher indemnity with the spread of disease at the time of evaluation, a patient who has metastasis and is alive, and a date of occurence closer to the present. Indemnity is less in patients who have had a lymph node dissection, who have died, or who are alive without metastasis. The WHP model predicts an increased overall indemnity with the spread of disease at the time of evaluation and the presence of a mass without pain. Indemnity decreases with a history of pregnancy, absence of presenting symptoms, or presentation with pain with or without a mass, and the performance of a lymph node dissection.