Investigation of 280 cases of systemic lupus erythematosus (SLE) admitted during 15 consecutive years to the "N. Gh. Lupu" Institute of Internal Medicine, Bucharest, revealed association of this disease with tuberculosis (tb) in 51 cases (19%). In most of these patients, tb onset preceded that of SLE; in the others it was either concomitant or it occurred later, in the course of SLE evolution. It is assumed that tb is favouring SLE development, probably by antigenic oversollicitation in patients with genetic immune deficiencies. When it occurs in the late stages of SLE, association of tb is of severe prognosis.