Behcet disease is a multi-system disorder with still uncertain chemical causality. Chemical composition of molecules and elements in a human brain tissue of Behcet diseased patient is of interest. Time-of-flight secondary ion mass spectrometry is used to provide complex composition in Behcet disease and control tissues. Determined organic compounds are represented by fragments of carbohydrates, phospholipids, amino acids, and peptides in both samples without any qualitative differences. Trace heavy elements as Fe, Zn, and Cu are identified in Behcet disease tissue with increased intensities by only an averaged factor of 2.2 in comparison to the control. The significant differences between the control and Behcet disease tissues are in the presence of Si and Al. These two elements have significantly higher intensities by an averaged factor of 10.0 in Behcet disease tissue. The origin of Al and Si occurrence and the chronology of their accumulation are not clear, moreover this observation supports a significance of chemical characterization in an early stage of disease. (c) 2008 Elsevier B.V. All rights reserved.