Leukocyte adhesion to vascular endothelium is an early step in inflammatory damage to tissues. To investigate the expression of endothelial adhesion molecules in the inflammatory response associated with cardiopulmonary bypass, we measured messenger ribonucleic acid (mRNA) encoding the adhesion molecules E-selectin and intercellular adhesion molecule-1 in intraoperative samples of cardiac tissue and skeletal muscle from infants undergoing cardiopulmonary bypass. Atrial tissue samples were obtained before and after bypass from 11 children and paired samples of rectus abdominis muscle from 15. mRNA was analyzed by ribonuclease protection with the use of nonmuscle actin as an internal control. Atrial E-selectin mRNA levels increased from before to after bypass (median increase 3.5-fold, p = 0.0002) in each of nine patients tested, and atrial intercellular adhesion molecule-1 mRNA increased in seven of nine patients (median, 2.1-fold, p = 0.025). In skeletal muscle, E-selectin mRNA increased in 11 of 12 patients (median 4.3-fold, p = 0.0018), and intercellular adhesion molecule-1 mRNA levels increased in 13 of 13 patients (median 3.2-fold, p = 0.013). E-selectin and intercellular adhesion molecule-1 induction in skeletal muscle occurred with or without circulatory arrest. We conclude that adhesion molecule mRNA induction occurs in cardiac and noncardiac tissue during cardiopulmonary bypass in man.