In the context of a population-based case-control study in Italy, the authors investigated the possible association between the personal use of hair dyes and non-Hodgkin's lymphoma (NHL), leukemia, multiple myeloma, and Hodgkin's disease. They collected all incident cases of hematolymphopoietic malignancies; the control group was formed with a random sample of the general population. Overall, the authors interviewed 2,737 research subjects and 1,779 control subjects. Among women, the authors found no association between ever using hair dyes and the risk of hematolymphopoietic malignancies. However, for permanent hair dyes, the authors observed a slightly increased risk of lymphocytic leukemia (odds ratio [OR] = 1.3; 95% confidence interval [CI] = 0.8-2.2) and of follicular subtypes of NHL (OR= 1.3; 95% CI = 0.8-2.0). Women who used black hair dye colors were at an increased risk of developing leukemia (OR = 1.9; 95% CI = 1.0-3.4), in particular chronic lymphocytic leukemia (OR = 3.0; 95% CI = 1.1-7.5). In spite of the lack of information on the timing and frequency of hair dye use and the imprecision of the ORs, associations were suggested between leukemia and permanent black hair dye use and follicular NHL and the use of permanent hair dyes.