We compared the levels of soluble adhesion molecules E-selectin (sE-selectin), intercellular adhesion molecule-1 (sICAM-1) and vascular cell adhesion molecule-1 (sVCAM-1) alongside von Willebrand factor (vWf), CRP and rheumatoid factor in 40 patients with RA, 38 with systemic sclerosis (SSc), 35 with vasculitis and in 80 asymptomatic controls. Adhesion molecules were measured in serum by ELISA, rheumatoid factor by sheep red blood cell agglutination and CRP by immunonephelometry. Compared to controls, increased sE-selectin was found in patients with RA (P = 0.0015), vasculitis (P = 0.0003) and SSc (P = 0.0126), whilst raised sICAM-1 was found in RA (P < 0.0003), vasculitis (P < 0.0003) and SSc (P < 0.0378). sVCAM was lower in RA than in controls (P = 0.0102), but was unchanged in vasculitis or in SSc. vWf was raised in RA (P = 0.0102), vasculitis (P < 0.0003) and SSc (P < 0.0003). In a Spearman's rank analysis of all the data, vWf correlated with sVCAM-1 and sICAM-1 (both P < 0.001), sE-selectin with sICAM-1 (P < 0.001) and sVCAM with sICAM-1 (P < 0.005). Levels of rheumatoid factor correlated with those of sE-selectin (P = 0.003) and sVCAM-1 (P < 0.012), but there were no correlations between any index and CRP. The strongest correlations within the RA group were between sICAM and sVCAM (P = 0.001), in vasculitis it was between sE-selectin and sICAM (P < 0.001), and in SSc it was between sE-selectin and sVCAM (P = 0.019). These data suggest that the differing levels of vWf, sE-selectin and sICAM-1 in the inflammatory vasculitides may be useful in establishing a rolefor leucocyte/endothelial adhesion in these diseases.