The clinical significance of the DNA-malignancy grade (DNA-MG) was tested in 90 malignant lymphoma patients. Feulgen stained imprint smears from freshly cut lymph-nodes were investigated. DNA measurements were performed using various cytophotometers. The scalar DNA-MG, ranging from 0.1 to 3.0, was calculated from the variance of the tumor cells around the 2c peak. Except for the CLL, all entities of the Kiel classification for non-Hodgkin's malignant lymphomas showed considerable variation of the DNA-MGs. The DNA-MG, the age of the patients and the response to treatment were seen to have a significant influence on the survival time of non-Hodgkin's lymphoma patients. In high grade lymphoma patients of the Kiel classification, the DNA-MG was found to provide additional prognostic information. The DNA-MG was strongly correlated with the ESR, low albumin concentration, low lymphocyte counts in peripheral blood, clinical and pathological staging, and the response to treatment.