BACKGROUND: There has been no report on the clinical features or natural history of autoimmune hemolytic anemia (AIHA) in the Korean adult population. This study retrospectively analyzed the clinical characteristics and long-term outcomes of AIHA in the Korean adults. METHODS: Patients newly diagnosed with AIHA between January 1994 and December 2010 at Chungnam National University Hospital were enrolled. Patient characteristics at diagnosis, response to treatment, and the natural course of the disease were documented. RESULTS: Thirty-two patients (31 females and 1 male) with a median age of 48 years (range, 17-86) were enrolled. Of these, 21.9% were initially diagnosed with secondary AIHA. Thirteen patients (40.6%) were initially diagnosed with Evans' syndrome. Of the 29 patients who were placed on therapy, 27 (93.1%) showed a partial response or better. Nevertheless, 1 year after initiating treatment, 80% of the patients were still treatment-dependent. During follow-up (median length 14 months; range, 0.5-238), 14 of 25 patients (56.0%) who were initially diagnosed with primary warm antibody AIHA were found to have systemic lupus erythematosus (SLE). Median time to conversion to SLE was 8.0 months (95% CI, 4.3-11.7), and the probabilities of conversion at 12 and 24 months were 63% and 91%, respectively. Younger age (<60 years) and a positive fluorescent anti-nuclear antibody test were associated with a higher probability of SLE conversion (P=0.01 and P<0.001, respectively). CONCLUSION: Primary AIHA is rare. Regular, vigilant testing for SLE is required in patients initially diagnosed with AIHA.