Background: Up-to-date information concerning the optimal regimen assignment and sequencing of therapies is lacking for the treatment of mCRC patients. By tracking trends in treatment choice, this retrospective, observational study assesses current treatment patterns in mCRC patients by line of therapy. Methods: Using electronic medical record data from one of the largest US oncology databases (SDI), treatment regimens for 1L, 2L, and 3L were assessed for patients age =18 yrs diagnosed with mCRC from 1/1/04-7/31/11 who received anticancer agents. Results: 1,793 stage IV patients were identified in 1L, 1,050 in 2L, and 504 in 3L. Overall mean age was 60.4 yrs, and 54.6% were men. The most common comorbidities were hypertension (18.0%), lipid metabolism disorders (10.6%), and diabetes (8.6%). 47.8% had commercial insurance, 37.2% Medicare, 8.5% Medicaid, and 4.6% self pay. 1,026 patients received bevacizumab (B) in 1L, 583 in 2L, and 204 in 3L. Patients were more likely to receive FOLFOX (FX) + B in 1L and 2L. The top 3 regimens are shown in the table below. For patients who began treatment with B and continued B in a subsequent regimen, mean dose of B increased from 443.7 mg/kg (1L) to 567.0 mg/kg (2L) and 618.1 mg/kg (3L). Conclusions: FX is the regimen of choice in mCRC. In terms of biologics, B is more commonly used in 1L/2L than 3L. Given that approximately half the mCRC patients progressed to 2L/3L treatment, this likely reflects an unmet need for advanced therapies for the effective treatment of the disease. Furthermore, consistent dose escalation with continued B use across 2L/3L was seen despite that use of B in 3L mCRC is inconsistent with NCCN guidelines. Additional research on outcomes implications is needed, including mortality, patient toxicity, and costs.