To investigate the association of T cell activation with clinical exacerbations of RA, we measured serum levels of soluble interleukin-2 receptors (sIL2R), a marker of T cell activation, in serial samples obtained from 23 patients with RA. sIL2R measurements were performed on sera obtained from each patient every 2 weeks for up to 60 weeks, and levels were correlated with swollen joint counts, tender joint counts, physician global assessments, patient global assessments, pain scores, Health Assessment Questionnaire Disability Index scores, and Westergren erythrocyte sedimentation rates measured simultaneously. There were no significant correlations between changes in sIL2R levels and changes in any of the other measures, nor were lead-lag relationships detected, for the group as a whole. Examination of the time courses of individual patients revealed significant positive correlations between changes in sIL2R levels and changes in swollen joint counts in five patients; significant correlations with other measures were present in three or fewer patients. sIL2R levels also varied little over the 2-week time interval of greatest clinical change in each patient. These results suggest either that clinical exacerbations of RA are not associated with changes in T cell activation or that sIL2R levels do not accurately reflect such changes.