In the present work are performed the TG and DSC study of gallstone samples collected from patients submitted to cholecystectomy at the Hospital Universitario Onofre Lopes of Universidade Federal do Rio Grande do Norte, in Natal, Rio Grande do Norte State, Brazil. The gallstone samples were characterized by elemental analysis and infrared spectroscopy. Standard cholesterol was used for all analysis as comparison with the gallstones. Is verified that cholesterol is the main chemical component of all studied gallstone samples. The thermoanalytical study was performed on air and nitrogen atmospheres. The presence of cholesterol as the main chemical component of all gallstone samples is confirmed by TG and DSC results. (C) 2003 Elsevier B.V. All rights reserved.