Abstract Although several recent reports have discussed the similarities between human parvovirus B19 (HPV-B19) infection and systemic lupus erythematosus (SLE), the relationship between these conditions has not been established owing to the small number of patients investigated. In 1998-1999, an outbreak of Erythema infectiosum occurred close to our hospital, enabling us to investigate the clinical, hematological, and serological findings, including serum complement and antinuclear antibodies (ANA), in 22 patients with acute HPV-B19 infection. The principal symptoms included rash (86.3%), edema (59%), arthralgia (45.4%) and fever (31.8%). Lymphadenopathy was seen in three of the 22 cases. The laboratory findings showed high incidences of leukopenia (50%), hypocomplementemia (95%), and ANA (64.7%). At the time of disease onset, patients with acute HPV-B19 infection presented with features which were similar to those of SLE. The possibility of HPV-B19 infection should therefore be considered in patients presenting with SLE-like features.