Nonwhite patients are less likely than white patients to have their pain adequately treated. This study examined the influence of patient race and patient verbal and nonverbal behavior on primary care physicians' treatment decisions for chronic low back pain in men. We randomly assigned physicians to receive a paper-based, clinical vignette of a chronic pain patient that differed in terms of patient race (white vs. black), verbal behavior ("challenging" vs. "non-challenging"), and nonverbal behavior (confident vs. dejected vs. angry). We employed a between-subjects factorial design and surveyed primary care physicians (N=382), randomly selected from the American Medical Association Physician Masterfile. The primary dependent measure was the physician's decision as to whether (s)he would switch the patient to a higher dose or stronger type of opioid. Logistic regression was used to determine the effects of patient characteristics on physicians' prescribing decisions. There was a significant interaction between patient verbal behavior and patient race on physicians' decisions to prescribe opioids. Among black patients, physicians were significantly more likely to state that they would switch to a higher dose or stronger opioid for patients exhibiting "challenging" behaviors (e.g., demanding a specific narcotic, exhibiting anger) compared to those exhibiting "non-challenging" behaviors (55.1%). For white patients there was an opposite pattern of results in which physicians were slightly more likely to escalate treatment for patients exhibiting "non-challenging" (64.3%) vs. "challenging" (54.5%) verbal behaviors. Results point to the need for better understanding of the way a complex interplay of non-clinical characteristics affects physician behavior in order to improve quality of pain management and other clinical decision-making.