In this paper, we apply nonlinear techniques (Self Organizing Maps, k nearest neighbors and the k means algorithm) to evaluate the official Spanish mutual funds classification. The methodology that we propose allows us to identify which mutual funds are misclassified in the sense that they have historical performances which do not conform to the invest ment objectives established in their official category. According to this, we conclude that, on average, over 40% of mutual funds could be misclassified. Then, we propose an alternative classification, based on a double step methodology, and we find that it achieves a significantly lower rate of misclassifications. The portfolios obtained from this alternative classi fication also attain better performances in terms of return/risk and include a smaller number of assets.