Opioids are important in the management of pain in patients with cancer. Clinicians and patients are sometimes concerned about the effect of opioids on survival, which might decrease opioid prescription, compliance, and symptom control. We wanted to determine whether opioid analgesia was associated with shorter survival in adult patients with cancer. We systematically searched for studies that assessed the effect of regular systemic opioid analgesia on survival. We identified 526 unique records, with 20 articles meeting inclusion criteria. Thirteen end-of-life studies, including 11 very low-quality retrospective studies, did not find a consistent association between opioid analgesic treatment and survival; this evidence comes from low-quality studies, so should be interpreted with caution. Seven longer-term studies, including three randomised controlled trials and two prospective studies, were included. Six of these studies indicated that opioids were likely to be associated with a shorter survival. None of these studies were powered to assess the effect of opioids on survival as a primary endpoint. In view of this, no definitive conclusions can be made as to whether opioids affect survival in patients with cancer. These data suggest that while opioid analgesia does not affect survival at the end of life, in the context of longer-term treatment, higher-quality studies, with survival as a primary endpoint, are needed to confirm an independent association between opioid analgesia and shorter survival. An important limitation of research in this field is that the relationship between greater analgesic requirements and shorter survival may be mediated by painful progressive cancer.