Objective. To determine predictors of the occurrence of systemic lupus erythematosus (SLE) in patients with early (< 1 yr) undifferentiated connective tissue disease (CTD). Methods. Analysis of a cohort of 213 patients with early undifferentiated CTD at entry, followed for 5 yrs at 11 tertiary centers. Baseline demographic, clinical, and laboratory data were compared using univariate and Cox multivariate regression analyses to identify possible predictive features for the subsequent occurrence of SLE. Results. 143 of 213 patients had ascertainable clinical status at 5 yrs. By univariate analyses those who evolved to SLE (13%) were more likely to be younger, African-American, and to have alopecia, serositis, discoid lupus, positive Coombs' test, positive anti-dsDNA and anti-Sm antibodies, positive ANA (homogeneous pattern), and/or a false positive test for syphilis. Discoid lupus (relative risk = 15.8), serositis (4.1), ANA-homogeneous (4.8), and anti-Sm positivity (28.2) were retained as predictors of the occurrence of SLE in the Cox regression model. Conclusion. Some clinical and laboratory features in patients with early undifferentiated CTD can predict the subsequent occurrence of SLE.