16018 Background: Second opinions (SO) are common in medical practice. Aside from case series, little evidence exists to demonstrate a clinical benefit associated with SO. Lack of relevant data limits knowledge of numbers of patients, diseases, and motivations of SO seekers. Within the field of medical hematology/oncology (H/O), no specific demographic data are available to characterize patients seeking SO in the United States. Methods: To typify such patients at Mayo Clinic in Arizona (MCA), we recorded demographic and disease-related information for patients seeking these evaluations over a six month period from 1/1 through 6/30/05. Results: A total of 683 patients contacted MCA for medical H/O SO over the 6 month study period. A complete set of demographic and disease-related information was obtained from 655 patients; the remainder were excluded from the data set. Demographically, the majority of patients were female (53%), married (66%), and lived nearby (i.e., from Arizona-58%, or bordering state-22%). Average age was 62.3 years. Among oncologic diagnoses, the majority of patients (60% of 374 reported oncologic diagnoses) stated a diagnosis of breast, lung, colorectal, pancreatic or prostate cancer. Approximately 1/3 of patients had metastatic disease at the time they sought evaluation at MCA. There were 278 patients seeking evaluation for hematologic abnormalities, with the majority (160 patients, 58%) seeking evaluation for non-malignant conditions. Of those with malignancies, lymphoma (including Hodgkin and non-Hodgkin) was the most common (45%), followed by multiple myeloma (21%) and chronic lymphocytic leukemia (15%). Conclusions: This study provides insight into demographics and disease processes of patients seeking medical H/O SO at a tertiary care center in the United States. Although no definite conclusions can be drawn about motivations for seeking H/O SO, future research should examine patient motivation to better understand factors leading to this behavior. Given a lack of evidence for clinical benefit associated with SO seeking, and its potential costliness, better knowledge of demographic and motivational factors may allow for a more constructive approach to be taken toward the needs of SO seekers. No significant financial relationships to disclose.