B-cell activation factor from the tumor necrosis factor family (BAFF) is a key survival factor during B-cell maturation — a delicate immune checkpoint for B cells. Excessive BAFF production at this stage corrupts B-cell tolerance and leads to autoimmunity. Elevated serum BAFF levels have been detected in some patients suffering from various autoimmune conditions. The positive outcomes of currently ongoing clinical trials using BAFF-neutralising agents confirm that this factor plays a major pathological role in rheumatoid arthritis and in systemic lupus erythematosus. Almost a decade after its discovery, BAFF continues to occupy the main stage in Immunology, with more than one hundred BAFF-related articles published per year. In recent years, our understanding of cell signaling and autoimmune mechanisms in this system have seen major advances, refining new possibilities for therapeutic intervention.