We determined the serum levels for circulating adhesion molecules (circulating intercellular adhesion molecule-1 [cICAM-1], circulating endothelial leukocyte adhesion molecule-1 [cELAM-1], and circulating L-selectin [cL-selectin]) and circulating tumor necrosis factor receptor (cTNF-R) p60 in 29 patients with relapsing-remitting MS serially over a period of 12 months. During this period there were 27 relapses in 14 patients (48%). There was progression of disease activity in 12/25 patients (48%), as assessed by the occurrence of new lesions on nonenhancing, T2-weighted MRIs of the head. Clinically active patients with relapse or disease progression on MRI (n = 18) had frequent fluctuations in their serum levels for cICAM-1 if compared to patients with stable MS (n = 11). There were significant differences in the cumulative cICAM-1 production between the two groups (502 +/- 218 ng/ml in active versus 225 +/- 82 ng/ml in stable MS patients; p < 0.001). cTNF-R p60 serum levels were higher in patients with stable compared to active disease (2.3 +/- 0.5 ng/ml versus 1.5 +/- 0.6 ng/ml; p < 0.005). A significant increase in cICAM-1 levels was present at the time of a relapse (799 +/- 263 ng/ml versus 449 +/- 95 ng/ml; p < 0.001), whereas the highest serum levels for cTNF-R p60 occurred 4 weeks after the onset of a relapse (1.8 +/- 0.5 ng/ml at relapse versus 2.3 +/- 0.6 ng/ml 4 weeks after a relapse; p < 0.01). Interestingly, the cL-selectin serum levels in all MS patients were significantly higher than in healthy donors, whereas there were no differences for cELAM-1. These results reflect distinct changes of inflammatory variables in serum of patients with MS and revealed that cICAM-1 is an indicator for disease activity and that high serum levels for cTNF-R p60 are associated with remission.