We assessed the blood interleukin 11 (IL-11) levels in patients with disseminated intravascular coagulation (DIC). The IL-11 level exceeded the detection limit, i.e., IL-11 was positive, in 14 of the 21 patients in the group with DIC complicated by sepsis, with a mean value of 20.4 pg/ml. In the group with DIC uncomplicated by infection, IL-11 levels were above the detection limit in 8 of the 17 patients, and the average level was 10.6 pg/ml. The difference between the IL-11-positive rate in the two groups was not significant. Although IL-11 levels tended to be higher in the group with sepsis as a complication, the difference was not significant. The elevated IL-11 levels observed in patients with DIC, with or without complication by infection, seem quite appropriate as a biological response to increased platelets.