To validate the Russian version of the Brief Pain Inventory (BPI-R) and to examine predictors of inadequate pain management, 221 Russian patients with advanced-stage hematological malignancies or solid tumors completed the BPI-R and a Russian-language Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36-R). Factor analysis of the BPI-R found two underlying constructs, pain severity and pain interference, with Cronbach alphas of 0.93 and 0.95, respectively. Concurrent validity was established by comparing BPI-R items with SF-36-R scales. The BPI-R detected significant differences in pain severity and interference levels by Eastern Cooperative Oncology Group (ECOG) performance status, supporting known-group validity. Determination of the Pain Management Index revealed that 68% of the patients were inadequately treated by World Health Organization standards. Having advanced-stage disease and not receiving chemotherapy predicted inadequate pain management in a multivariate logistic regression model. The Russian version of the BPI is psychometrically sound in its reliability and validity.