Literature on the role of chemicals in the development of chronic lymphocytic leukaemia (CLL) and monoclonal B-cell lymphocytosis in humans is sparse. This research is complicated by the rarity of these outcomes and the different disease classifications used over time. Several studies have noted excesses of CLL among farmers and a few have pointed to specific chemicals. Reports suggesting elevated CLL rates in the rubber and petroleum industries point to a possible role for solvents and other chemicals. The few studies that focus on specific chemicals suggest that CLL should be more carefully evaluated in relation to possible exposure to chemicals and solvents, particularly for benzene and butadiene. Pooled analyses of CLL studies within consortia offer an opportunity to investigate the possible aetiological role of chemical exposures with improved statistical power.