147 Copyright © 2010, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 7 Classifcation with Incomplete Data Pedro J. García-Laencina Universidad Politécnica de Cartagena, Spain Juan Morales-Sánchez Universidad Politécnica de Cartagena, Spain Rafael Verdú-Monedero Universidad Politécnica de Cartagena, Spain Jorge Larrey-Ruiz Universidad Politécnica de Cartagena, Spain José-Luis Sancho-Gómez Universidad Politécnica de Cartagena, Spain Aníbal R. Figueiras-Vidal Universidad Carlos III de Madrid, Spain ABStrAct Many real-word classifcation scenarios suffer a common drawback: missing, or incomplete, data. The ability of missing data handling has become a fundamental requirement for pattern classifcation because the absence of certain values for relevant data attributes can seriously affect the accuracy of classifcation results. This chapter focuses on incomplete pattern classifcation. The research works on this topic currently grows wider and it is well known how useful and effcient are most of the solutions based on machine learning. This chapter analyzes the most popular and proper missing data techniques based on machine learning for solving pattern classifcation tasks, trying to highlight their advantages and disadvantages. DOI: 10.4018/978-1-60566-766-9.ch007