OBJECTIVES: CLL is an indolent incurable lymphoma with a widely variable disease course.  Its treatment is therefore quite heterogeneous.  The goal of this project was to evaluate the real-world use of individual agents or combination regimens across all lines of therapy in CLL during the years 2010-2013 in order to understand the current treatment paradigm of CLL. METHODS: Treatment records for 110,000 cancer patients and over 6.7 million drug administrations were evaluated between August 2010 and July 2013 at US cancer care facilities participating in a nationwide, commercially available chemotherapy order entry system called IntelliDose®.  IntelliDose® captures patient demographics, stage, and details of chemotherapy treatment.  The composition of the 820 oncologists who use IntelliDose® is much like the overall population of oncologists in the US, including 54% in private practice and 41% community hematologist/oncologists. The CLL patients sampled by IntelliDose® were projected to a national level for the interpretation of the results. RESULTS:  The average monthly number of CLL patients undergoing any line of treatment was 7,736 (SD= 565). Of the 3,380 patients receiving first line therapy, the majority of patients (n=810; 24%) were receiving Bendamustine-Rituximab (BR), followed by Fludarabine- Cyclophosphamide -Rituximab (FCR) (n=716; 21%).For relapsed CLL, BR was also the most common regimen (18-33% of monthly use), followed by R monotherapy (7- 16% of monthly use). Across all lines of therapy, BR is the most common regimen used (14-32% monthly use) followed by R alone as the second most common regimen (18-25% of monthly use) CONCLUSIONS: Rituximab is the most frequently used agent either as a single agent or in combination, in all lines of CLL treatment in the US.  Single agent Rituximab is commonly used in CLL therapy in 2^nd line and above, despite low reported response rates in the literature.