SLEDAI, a disease activity index for systemic lupus erythematosus (SLE) has been validated against other such indices and its reliability has been shown by specialists in SLE. To assess its reliability among less experienced clinicians, we conducted a reliability study with 3 rheumatology trainees and 9 patients with SLE according to a Latin square design. SLEDAI easily distinguished between patients (p = 0.0009), and physician variability was not statistically significant (p = 0.27). Inter and intraobserver agreement were 78.7 and 98.0%, respectively. SLEDAI was thus shown to be a reliable instrument among less experienced observers for the assessment of disease activity in SLE.