High Computational Complexity of the Decision Tree Induction with many Missing Attribute Values Rafal Latkowski Institute of Computer Science, Warsaw University ul. Banacha 2, 02--097 Warsaw, Poland rlatkows@mimuw.edu.pl Abstract The decision tree induction is a widely applied technique in machine learning. Algorithms based on such technique with careful implementation can reach the computational complexity Omega(n*log(n)). However, a special treatment of decision trees is needed in case of missing values. The most popular and widely used approach to this problem is to divide such cases among all subsets (sub-nodes). Such an approach is implemented, e.g., in C4.5, RSES-Lib, WEKA and many other machine learning programs. In this paper we show that this strategy leads to a significant increase (O(n^gamma)) of computational complexity of the decision tree induction algorithm for data sets with many missing values.