We studied the effects of escalating doses of recombinant human IL-1 beta in patients receiving high-dose chemotherapy and ABMT for metastatic breast cancer or malignant melanoma. Sixteen patients received IL-1 beta, 4 to 32 ng/kg/day administered subcutaneously for 7 days beginning 3 h after bone marrow infusion. Three patients at the highest dose level also received G-CSF following completion of IL-1 beta. All patients completed the 7 days of therapy. The majority of patients experienced chills and fever following one or more injections, and seven had severe pain at the injection site. There was one episode of hypotension and one episode of transient confusion at the highest dose level; other significant toxicity was not identified. Recovery of neutrophils to > 0.5 x 10(9)l and platelet transfusion independence occurred at a median of 23 and 22 days, respectively, which was comparable to historical controls. The mean number of bone marrow colony-forming unit granulocyte-macrophage (CFU-GM) per 10(5) mononuclear cells on day +21 post-ABMT was more than twice that of control patients or patients receiving G-CSF or GM-CSF. A linear correlation was found between the dose of IL-1 beta and endogenous concentrations of several cytokines. These patients also displayed significantly higher concentrations of endogenous G-CSF compared to historical controls receiving GM-CSF. While IL-1 beta was moderately toxic and had no effect on recovery of peripheral blood counts after ABMT, the increased number of bone marrow CFU-GM suggests that the addition of G- or GM-CSF to a short course of IL-1 beta may accelerate hematologic recovery.