OBJECTIVES: Treatment with strong opioids is connected with frequent and problematic side effects where one of the most common is Opioid Induced Constipation (OIC). The discomfort of OIC can limit an effective pain therapy. Further, little is known about the cost implications of OIC. The objective of this study was to estimate the direct and indirect costs for patients with  OIC after treatment with strong opioids. METHODS: The study is based on patient data from a Swedish non-interventional, follow-up study, UPPSIKT  (UPPföljning Starka opioider I Klinisk Terapi). The cost analysis is based on 197 patients treatmed with strong opioids during a six-month period. Direct and indirect costs are calculated per patient month and the cost for constipation is estimated as the difference between patient months with and without constipation. RESULTS: Around 60-70% of the patients reported to experience some degree of problem with constipation each month. The total number of patient months with no, mild, moderate and severe constipation were 419, 302, 288 and 135 months respectively. The total costs per patient month with severe problems with constipation were significantly higher than for patients with mild, moderate or no constipation. Patients with severe constipation had the highest total costs, 14,639 SEK per patient month, while patients with mild, moderate and no problems have 11,481 SEK, 10,443 SEK and 9,924 respectively. Patients with severe constipation reported on average a lower quality of life compared to the other patients in the study. CONCLUSIONS: The results from our cost analysis indicate that constipation associated with opioid use has the potential to increase the costs to society. The study also concludes that patients with severe constipation experience a lower quality of life than patients with fewer problems.