Clinical and prognostic studies were carried out in a series of 143 patients with low-grade (small-lymphocytic, follicular small cleaved cell, follicular mixed small- and large-cell) lymphoma. After treatment with alkylating agents (21.5% cases), combination chemotherapy (73.3%) or other therapies (5.2%), complete response (CR) was obtained in 40.7% of cases and partial response (PR) in 43.7%. The stage of the disease was the most important factor for response. With a median follow-up of 6.5 years, 48.0% (95% Cl: 37.5-58.5) of patients were alive 10 years after diagnosis. Among the initial parameters, advanced stage. B-symptoms, poor performance status, nodal involvement > 3 sites, extranodal involvement > or = 2 sites, WBC count > or = 10 x 10(9)/L, leukemic expression, high serum LDH levels, and bone marrow infiltration were all related to survival; treatment modality, however, had no influence on survival. In the multivariate analysis, stage (p = 0.008) and age (p = 0.053) were the most important prognostic factors. When considering response to therapy, both CR (p < 0.001) and PR (p = 0.003) emerged as the most important predictive variables, with only the absence of B-symptoms retaining its prognostic significance (p = 0.014) among the other parameters. In addition, in CR patients the duration of the response (< or = 1 year vs. > 1 year) was the most significant parameter for survival (p < 0.001). Finally, the initial stage (p = 0.011) and the histologic subtype (those patients with follicular mixed lymphoma relapsing less frequently than the others) (p = 0.052) were the only significant factors for relapse.