To determine the plasma and saliva levels of IL-6 in patients with bisphosphonate-related osteonecrosis of the jaws (BRONJ) and to investigate whether there is a correlation between more advanced stages of BRONJ and levels of IL-6. We studied three groups: group 1 consisted of 30 patients with BRONJ due to intravenous bisphosphonates (ivBP), group 2 consisted of 25 patients treated with ivBP but without BRONJ, and group 3 consisted of 15 healthy controls. In each case, we assayed plasma and saliva IL-6 samples using an ELISA test. Significantly, higher IL-6 values were found in both saliva and plasma in group 1 vs groups 2 and 3 (P<0.01). Group 1 showed no differences in plasma or saliva IL-6 according to patient gender (P>0.05), type of tumor, BRONJ location, etiology of BRONJ, or disease stage (P>0.05). We found higher plasma and saliva IL-6 values in the more advances stages of BRONJ, although the differences were not statistically significant. Plasma and saliva IL-6 values were higher in our patients with BRONJ than in controls and therefore might be a useful tool for monitoring the severity of BRONJ.