OBJECTIVES: I. Determine the complete and partial response rates in patients with newly diagnosed or relapsed indolent non-Hodgkin's lymphoma, high risk chronic lymphocytic leukemia, or prolymphocytic leukemia treated with irinotecan. II. Determine the toxicity of this regimen in these patients. III. Correlate the level of DNA topoisomerase I mRNA and protein, as well as SN-38 induced topoisomerase I-DNA complex formation, with the clinical response and toxicity in these patients. IV. Determine if a down regulation of topoisomerase I or altered subcellular distribution of this enzyme is involved in the drug resistance to irinotecan.