Description: This paper models minimum pension guarantee using a simulation approach. Lachance and Mitchell [2002] have shown that it could be important if and when individual accounts are introduced in the United States. This paper's model uses real data from Mexico where individual accounts are already a reality and the minimum pension guarantee is already enshrined by law. The authors calculate the probability of the government needing to honor the guarantee and estimate the cost of such a promise using a real options approach. Higher investment in the stock market turns out to be the key. The higher the proportion of investment allowed by law in stocks, the lower the probability of government support.