A multivariate survival analysis by means of Cox's multiple regression model was performed on a series of 150 consecutive patients with chronic lymphocytic leukemia (CLL) from a single institution. In addition to the well established prognostic factors, such as anemia and thrombocytopenia, a marked prognostic value of the degree of absolute peripheral lymphocytosis emerged from this analysis. This was evident in the whole population as well as in low and intermediate risk groups of patients (Rai's stages 0, I, and II and International Workshop on CLL stages A and B), pointing out that different subsets of patients can be isolated within these groups.