224 Int. J. Computational Biology and Drug Design, Vol. 1, No. 3, 2008 Copyright © 2008 Inderscience Enterprises Ltd. Consensual classification of drug and nondrug compounds Ayca C. Pehlivanli Computer Engineering Department, Istanbul Kultur University, Atakoy, Istanbul, Bakirkoy, 34156, Turkey E-mail: a.pehlivanli@iku.edu.tr Turgay Ibrikci Department of Electrical Electronics Engineering, Cukurova University, Balcali, 01330, Adana, Turkey E-mail: ibrikci@cu.edu.tr Okan K. Ersoy* School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA E-mail: ersoy@purdue.edu *Corresponding author Abstract: A special consensual approach is discussed for separating a molecular group with a proven pharmacological activity from another molecular group without any activity. It is mainly a group decision to produce a consensus of multiple classification results obtained with a single classification algorithm. For this purpose, the constructed model has a preprocessing unit which consists of transformation of input patterns by random matrices and median filtering to generate independent errors for a single type of classifier and postprocessing for consensus. The neural network based consensus classifier operating with MOE descriptors was applied to a set of 641 chemical structures. The confirmed drugs were classified with an accuracy of 86.54% while nondrugs resulted in 82.67% accuracy. Keywords: classifier design and evaluation; neural nets; drug design; nondrug; classification. Reference to this paper should be made as follows: Pehlivanli, A.C., Ibrikci, T. and Ersoy, O.K. (2008) ‘Consensual classification of drug and nondrug compounds’, Int. J. Computational Biology and Drug Design, Vol. 1, No. 3, pp.224–234. Biographical notes: Ayca C. Pehlivanli received the BS Degree in Statistics from Hacettepe University in 1997 and the MS Degree in 2001 from Syracuse University, Syracuse, USA in the field of computer and information science. She received her PhD Degree from the Department of Electrical Electronic Engineering at Cukurova University. She has been involved in research