Guidelines currently exist on the use of opioid therapy for chronic nonmalignant pain. Unfortunately, no randomized, prospective, controlled studies have been conducted to verify these guidelines or determine the optimal inclusion or exclusion criteria for this treatment. The decision to administer opioid therapy is often based on treatment orientation and subjective clinical impressions. This article contains two sections relevant to assessment for chronic opioid therapy in nonmalignant pain. First, a brief review of the literature on opioid therapy is presented. Survey data on opioid use and follow-up helpfulness are also presented. Second, current guidelines for opioid therapy are discussed, and areas considered critical in assessing treatment efficacy are reviewed, including (1) pain intensity, (2) functional capacity, (3) personality and mood, (4) pain beliefs, (5) medication usage, (6) adverse effects, (7) health-care utilization, and (8) medical and psychosocial history. Finally, questions are posed for future investigations of the efficacy of opioid therapy in selected patients with chronic nonmalignant pain. This article identifies important areas to consider when initiating controlled trials designed to identify those patients most suitable for chronic use of opioids.