The results of experimental studies suggest that cytoreduction has important potential benefits. In the laboratory setting, reduction of tumor burden increases the sensitivity of remaining tumor to chemotherapy and radiation therapy by increasing the proportion of proliferating tumor cells, by decreasing the number of necessary chemotherapeutic cycles necessary to eradicate the tumor, by improving cellular distribution of oxygen and nutrient within the tumor and by reducing the likelihood that resistant clones will develop. The evidence for clinical benefit seems much more limited. In general, a benefit of cytoreduction in extending the survival or disease-free interval appears likely only if there is effective chemotherapy or radiation therapy. Hence, benefits of cytoreduction have been acknowledged in pediatric solid tumors, lymphoma and carcinoma of the ovary, for which effective adjuvant treatments exist. Patients with certain tumors that exhibit biologically favorable characteristics may benefit from cytoreduction, even though the usefulness of other treatment modalities may be minimal. (ABSTRACT TRUNCATED AT 250 WORDS)