In rheumatoid arthritis (RA) the adhesion molecule ICAM-1 mediates the adhesion of leucocytes following subsequent transendothelial migration including interactions and adhesion of several cell types such as fibroblasts, T-lymphocytes and synoviocytes. Significantly increased ICAM-1 levels were measured in the acute phase of RA. The correlation of ICAM-1 levels with the pteridine neopterin (p < or = 0.01) may reflect the role of this adhesion molecule in modulation of immune responses. Despite the significantly higher levels of acute phase reactions parallel to the elevated ICAM-1 levels, no correlations were found between ICAM-1 and erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and serum-Amyloid A (SAA). During an in-patient multidisciplinary rehabilitation programme the levels of ICAM-1 in serum and the majority of all investigated laboratory and clinical parameters such as ESR, CRP, SAA, fibrinogen, pain, swollen and painful joint count, morning stiffness and health assessment questionnaire improved.