BACKGROUND Soluble forms of intercellular adhesion molecule-1 (sICAM-1) and vascular cell adhesion molecule-1 (sVCAM-1) have recently been identified in serum samples from atopic patients, but their clinical significance in the treatment of allergic diseases remains to be established. OBJECTIVE To study the clinical roles of serum sICAM-1 and sVCAM-1 during immunotherapy for perennial allergic rhinitis. METHODS Our study included 30 nonatopic volunteers and 60 patients with perennial allergic rhinitis due to Dermatophagoides farinae. The 60 patients had been treated for variable periods (7.3+/-3.0 years [mean+/-SD]) with immunotherapy using a standardized D. farinae antigen. Serum samples were collected from each patient before and after immunotherapy to determine sICAM-1 and sVCAM-1 with sandwich enzyme-linked immunosorbent assays. RESULTS Serum levels of sICAM-1 in the patients before immunotherapy were higher than those in the nonatopic volunteers (P<.001). The levels of sICAM-1 in the patients' serum samples were decreased significantly after immunotherapy (P<.001), and the percentage of the decrease in the sICAM-1 levels was significantly correlated with the duration of immunotherapy (P=.04) and with the percentage of the decrease in symptom scores (P<.001). The levels of sVCAM-1 in the serum samples from the patients with severe symptoms were significantly higher before immunotherapy than those in the nonatopic volunteers (P=.002) and were significantly decreased after immunotherapy (P=.05). However, the percentage of the decrease in the sVCAM-1 levels was not correlated with the duration of immunotherapy (P=.89) or with the percentage of the decrease in symptom scores (P=.89). CONCLUSIONS Decrease in serum sICAM-1 levels during immunotherapy is probably involved in the working mechanisms of immunotherapy, but modulation of serum sVCAM-1 levels is not likely related to the clinical effect of immunotherapy.