We utilized data from two Kaiser Permanente medical care programs to evaluate risks of hematopoietic and lymphoproliferative (HLP) malignancies after use of 14 common medications. The subjects were adult cases of non-Hodgkin's lymphoma (NHL) (N = 94), multiple myeloma (N = 159), and leukemia (N = 257) and individually matched controls (N = 695). Abstractors reviewed medical records and recorded medication notations. Using a minimum 5-year exposure lag between first notation and malignancy diagnosis, the risk of NHL was greater among plan members who were prescribed amphetamines [odds ratio (OR) = 2.2; 95% confidence interval (CI) = 1.1-4.8], lidocaine (OR = 2.6; 95% CI = 1.2-5.5), and meprobamate (OR = 2.1; 95% CI = 1.03-4.3). The risk of NHL rose with increasing number of medical record notations for amphetamines; however, there was no association with number of notations for lidocaine or meprobamate. The odds ratio for total leukemia was decreased among patients who took chloramphenicol (OR = 0.4; 95% CI = 0.2-0.97).