The mononuclear cells and plasma in bone marrow from 30 subjects with leukemia, 12 subjects with hematological disease, four subjects with multiple myeloma, one subject with malignant histiocytosis and 18 normal subjects were analyzed by high-resolution Py-CC(HR Py-GC). In the present study, the samples were pyrolyzed using CDS 122 pyroprobe at 770 degrees C, coupled on-line to a model HP 5890A gas chromatograph with a fused silica capillary column coated with PEG 20M. The results showed that the pyrograms of the leukemia cases were significantly different from those of the other hematological diseases and normal subjects. A characteristic peak with the same retention time in the pyrograms of the leukemia, multiple myeloma and malignant histiocytosis samples was found. In contrast, this characteristic peak did not appear in the pyrograms of other hematological diseases and normal subjects. The pyrograms of the different subtypes of leukemia were also different. Variation in the pyrograms of six cases of mononuclear cells and plasma from different stages of treatment were closely related to changes in the effectiveness of the treatment. All pyrograms of the plasma from the leukemia, other hematological diseases and normal controls showed similar results to those of the mononuclear cells. Therefore, 36 clinical samples of the different subtypes of acute leukemia were identified by the method, 35 cases were diagnosed (97.2%). The technique appears to provide a simplified and reproducible method as a rapid diagnostic tool and dynamic observation of acute leukemia.