To elucidate the hematopoietic activity of recombinant human interleukin-11 (rhIL-11, [Neumega, Cambridge, MA]) in patients with cirrhosis and thrombocytopenia, we administered rhIL-11 at 50 microg/kg/d subcutaneously to 10 patients for 10 days with a 30-day follow-up period. All treated patients (n = 9) experienced a gradual, yet significant increase in their platelet count above the baseline value (P < or =.01) reaching the peak value (median, 93,000/microL; range, 60,000-206,000/microL) at a median of 13 days (range, 6-23 days). Eight patients (89%) had a significant increase of > or =50% over the baseline value (P <.05). Moreover, further increases to > or =60,000/microL, > or =80,000/microL, and > or =100,000/microL were observed in 100%, 78%, and 33% of the patients, respectively. A subsequent decline in platelet count was observed at a median of 19 days (range, 7-26 days) after the occurrence of peak concentration. A significant increase in neutrophil count was also demonstrated starting on the third day of treatment (P < or =.01). Concurrent with an increase in the serum level of fibrinogen, transaminase levels declined significantly during treatment period, while bilirubin levels continued to drop for up to 20 days after the initiation of treatment (P <.05). The most frequent effects were due to plasma volume expansion, including conjunctival redness and edema. In conclusion, rhIL-11 can improve platelet counts in patients with early cirrhosis and these patients could benefit from rhIL-11 treatment. However, given the high frequency of regimen-related toxicity, the use of rhIL-11 in patients with cirrhosis should be administered with caution.