This study aims to measure the ability to pay in projects financing PRONAF for peach production in Southern State of Rio Grande do Sul. The objective is identifying how prices fluctuations change the payment capacity of family farmers. We use the Montecarlo methods to perform simulations of variable price and as a result is obtained that thirteen projects in the sample have no ability to pay the proposed funding. The assessment of repayment capacity indicates that the requested amount of funding is high when compared with the gross production of peach. The price fluctuations also contribute to possible increases in delinquency PRONAF. An analysis considering the non-farm income of the production units would add to the capacity payment.