Patterns of opioid use, resource utilization, and costs in cancer patients with and without constipation were compared using retrospective insurance claims data. Inclusion criteria were > =30 days of opioid use and continuous plan coverage for > or =6 months before and > or =12 months following first opioid claim (index date). Constipation was defined as > or =1 ICD-9-CM diagnosis codes in the range of 564.0x during the 12 months postindex date. Of the 8836 opioid initiators with cancer initially considered, approximately 9.3% (n = 821) had a diagnosis of constipation during follow-up. Opioid use patterns were compared between patients with constipation and matched controls. Two-part semilogarithmic regression models assessed the impact of constipation on resource utilization and associated costs. Compared with controls without constipation, patients with constipation had higher rates of concurrent use of > or =2 opioids (P < .0001), opioid discontinuation (P = .0002), opioid switching (P < .0001), nausea with vomiting (P < .0001), and respiratory depression (P = .0003). Compared with controls, more patients with constipation received inpatient (P < .0001), hospice (P = .0086), home health (P < .0001), laboratory (P = .0015), other outpatient (P < .0001), emergency (P < .0001), office visit (P < .0001), and nursing home care (P = .0266). Compared with controls, patients with constipation had substantially higher total costs (P < .0001). This study suggests that in opioid-treated cancer patients, constipation significantly impacts opioid-use patterns, resource utilization, and costs. Alleviation of constipation may optimize opioid therapy and reduce costs.