The diagnosis of 'early inflamed', 'recurrent' or 'sub-acute' appendicitis is often difficult and accompanied by controversies between clinical data, histological findings, and their interpretation. The expression of the intercellular cell adhesion molecule-1 (ICAM-1), the vascular cell adhesion molecule-1 (VCAM-1), and E-selectin has been studied in 61 appendicectomy specimens for possible use as a diagnostic tool. This study demonstrates a different expression of CAM by endothelial (EC) and mesothelial cells (MC) in the various stages of appendicitis, with early E-selectin and ICAM-1 expression in EC, followed by VCAM-1 in EC and MC. Appendices from patients with prolonged clinical symptoms defined by clinicians as 'chronic' appendicitis showed VCAM-1 expression and occasionally weak expression of E-selectin in EC. In several cases, discrepancies were found between the pre-operative 'clinical' diagnosis, the histomorphological findings, and the immunohistological results. In this context, the expression of E-selectin and VCAM-1 in comparison with the histological features has potential significance in the diagnosis of 'early acute', 'sub-acute' or 'recurrent' appendicitis. In addition, a correlation was demonstrated between the histological stages of appendicitis and the kinetics of CAM expression. The study also indicates that the time course of E-selectin expression in vivo is longer than is suggested from in vitro data.