In this paper we discuss cost and pro-efficiency for a sample of financial institutions on the Colombian financial market in the period 1989-2003, using stochastic frontier efficiency analysis. During the period, the cost-efficient frontier deteriorates, but pro-efficient frontier is relatively stable. We found significant difference when we compare the efficiency scores between types of financial intermediaries. Additionally, our analysis shows that the scores for pro and cost efficiency have different distribution. We found big differences between pro and cost efficiency among the diferent type banks. This is evidence in favor of some banks behaving collusively and capturing oligopoly rents.