This book constitutes the refereed proceedings of the 6th International Symposium on Biological and Medical Data Analysis, ISBMDA 2005, held in Aveiro, Portugal, in November 2005. The 39 revised full papers presented were carefully reviewed and selected for inclusion in the book. The papers are organized in topical sections on medical databases and information systems, data analysis and image processing, knowledge discovery and data mining, statistical methods and tools for biomedical data analysis, decision support systems, collaborative systems in biomedical informatics, as well as computational models, structural analysis, and microarray data analysis in the scope of bioinformatics