OBJECTIVES: To elicit treatment preference and WTP for Methylnaltrexone, a novel peripheral opioid antagonist versus existing therapies for managing palliative care patients with Opioid Induced Constipation (OIC). METHODS: The study was conducted by developing and administering a survey composed of a modified decision board and a WTP instrument to subjects recruited from the general public in Ontario, Canada (N= 401). The decision board described the state of OIC, therapeutic options and the outcomes and side effects associated with each option. Participants stated their therapeutic preference and those who preferred methylnaltrexone were subsequently presented with a WTP instrument which elicited the hypothetical amount of money they would be willing to pay out-of-pocket per week and as additional monthly insurance premium for the therapeutic option that included methylnaltrexone. Kruskal-Wallis test, Wilcoxon Rank-Sum test, chi-square tests and multiple linear regression analysis were performed to assess the influence of demographics and other variables on treatment preference and WTP.  RESULTS: Majority of the participants (N=241) chose the methylnaltrexone plus laxative regimen as their therapeutic preference (60% vs. 36%, 4% indifferent). Treatment preferences were found to be significantly different between age groups (p<0.001) and education levels (p=0.021).  The mean WTP for out-of-pocket expenses per week was $163.42 with values ranging from $0 to $ 2308.  The overall mean additional monthly premium was $8.65.  Household income was a significant predictor of out of pocket amount (p<0.05). Other demographic parameters did not have a significant impact on WTP. CONCLUSIONS: In this study population, which determined the maximum WTP for treatment of OIC, most participants were willing to pay to have methylnaltrexone added to conventional therapies.  The WTP values need to be further incorporated in a formal cost benefit analysis.