What causes people to get chronic lymphocytic leukemia?

Mostly unknown: Cll affects older white men more that other parts of the population and the cause is unknown in most cases. Exposure to certain herbicides and insecticides, including agent orange used during the vietnam war, have been linked to an increased risk. For more information consult: http://www.Mayoclinic.Com/health/chronic-lymphocytic-leukemia/ds00565/dsection=risk.