Introduction: At present co-insurance (out of pocket payment) of insured parties in Iran for medicine prescriptions in outpatient ward equals to 30% of total cost of prescriptions. This amount of payment of co-insurance in those families with difficult to treat or chronic patients, causes to increase the encounter with catastrophic health costs. The goal of this research was to examine the willingness to pay of Social Security Organization insured for not encounter to catastrophic cost of medicine prescriptions.

Method: This cross sectional research was performed through interview based questionnaire in Esfahan Social Security Organizations insured society. The interviewees were randomly selected among head of households insured who referred to Esfahan's Quods Clinic. Contingent valuation method was used to evaluation the mean of willingness to pay of respondents. Validity and reliability of this method were verified through several studies. One way Anova and categorical regression in SPSS software were used for examination of variables relation and analysis of factors effected upon the amount of willingness to pay.

Results: Respondents were willing to pay 3496 Tomans (SD=2396) of medicine prescriptions costs for exemption from payment of prescriptions with prices more than100,000 Tomans.The results of categorical regression analys showed the maximum effect of income level upon the amount of willingness to pay.

Conclusion: Regarding to the mean evaluated of willingness to pay insurer organizations can increase the coverage of medicine prescriptions cost more than 100,000 tomans price, through decreasing the coverage of medicinal prescriptions with fewer prices than estimated WTP.