A study was conducted of the changes in lymphocyte cell surface antigens, lymphoblastogenesis response to mitogens, and differential white blood cell counts caused by occupational opiate exposure in factory workers. Thirty three morphine processing workers with complaints of work related dyspnea, wheezing, headache, malaise, tiredness and skin reactions were enlisted in the study. Eight workers with no known occupational opiate exposure were also included. Breathing zone air samples were taken and analyzed via high pressure liquid chromatography (HPLC) to determine levels of codeine (76573) and morphine (57272). No significant differences were seen in the hematologic parameters and immunoglobulin levels of the groups, except for an increase in the number of basophils present in the opiate exposed workers. Elevated levels of some species of B-cells and T-cells were also seen in this group, as was also a reduction in lymphocyte proliferation. The authors conclude that occupational opiate exposure effects changes in the profile of circulating peripheral blood leukocytes, or the expression of leukocyte surface receptors, but that the relevance of these changes to opiate induced asthma is still unclear.