The DNA content and S-phase fraction (SPF) of pathological paraffin-embedded lymph node tissue from 47 patients with poor prognosis non-Hodgkin's lymphoma (NHL) were analyzed by flow cytometry (FCM). Fifteen of 42 evaluable cases proved to be aneuploid. The DNA aneuploidy was not correlated with age, histology, stage, presence of systemic symptoms, clinical response or overall survival (OS) of patients. Mean SPF evaluated in 35 cases was 22.9%. After 78 months of follow-up, nine patients with diploid low SPF tumors had a significantly longer disease-free survival (DSF) with respect to the group of patients (33 cases) with aneuploid or diploid high SPF tumors (100% vs 59%; log rank test, p = 0.04).