Objective. To determine the prevalence and associations of antiendothelial cell antibodies (AECA) in a well characterized cohort of patients with idiopathic inflammatory myopathies (IIM). Methods. Clinical characteristics, AECA, and myositis-specific autoantibodies were assessed by standard methods in 56 subjects with IIM. Results. AECA were found in 20/56 patients with IIM, were seen in all the major clinical and serologic IIM groups, and were found in 10/15 patients with interstitial lung disease (ILD) (chi squared 6.5, p < 0.01 with Yates' correction, relative risk 2.7, specificity 86% and sensitivity 50%). Antisynthetase antibodies, also associated with ILD as described (chi squared = 26.5, p < 0.001 with Yates' correction, relative risk 8.7, specificity 95%, sensitivity 77%), did not correlate with the presence of AECA. Conclusion. AECA appear to be present in all forms of IIM and are markers for ILD that are independent of anti- synthetase autoantibodies. AECA may be a useful serologic marker for ILD in IIM.