A case-control study of adult-onset leukemia was conducted in Bangkok, Thailand to explore the contribution of cellular telephone use and other factors to the etiology of the disease; 180 cases (87 acute myeloblastic leukemia, 40 acute lymphoblastic leukemia, 44 chronic myelogenous leukemia, eight chronic lymphocytic leukemia, one unclassified acute leukemia) were compared with 756 age- and sex-matched hospital controls. Data were obtained by interview; odds ratios (ORs) were estimated by unconditional logistic regression. There was no clear association with cellular telephone phone use, but durations were relatively short (median 24-26 months), and there was a suggestion that risk may be increased for those with certain usage practices (ORs, 1.8-3.0 with lower confidence intervals >1.0) and those who used GSM service (OR, 2.1; 95% confidence interval, 1.1-4.0). Myeloid leukemia (acute and chronic combined) was associated with benzene (OR, 3.9; 95% confidence interval, 1.3-11), a nonspecific group of other solvents (2.3; 1.1-4.9), occupational pesticides that were mostly unspecified (3.8; 2.1-7.1), and working with or near powerlines (4.3; 1.3-15). No associations were found for diagnostic X-rays, cigarette smoking, or other occupational exposures.