Decision tree algorithms are very popular in the area of data mining since the algorithms have a simple inference mechanism and provide a comprehensible way to represent the model. Over the past years, fuzzy decision tree algorithms have been proposed in order to handle the uncertainty in the data. Fuzzy decision tree algorithms have shown to outperform classical decision tree algorithms. This chapter investigates a fuzzy decision tree algorithm applied to the classification of gene expression data. The fuzzy decision tree algorithm is compared to a classical decision tree algorithm as well as other well-known data mining algorithms commonly applied to classification tasks. Based on the five data sets analyzed, the fuzzy decision tree algorithm outperforms the classical decision tree algorithm. However, compared to other commonly used classification algorithms, both decision tree algorithms are competitive, but they do not reach the accuracy values of the best performing classifier. One of the advantages of decision tree models including the fuzzy decision tree algorithm is however the simplicity and comprehensibility of the model as demonstrated in the chapter.