In 2006, the Study Group on Autoimmune Diseases (GEAS) of the Spanish Society of Internal Medicine created the BIOGEAS project, a multicenter study devoted to collecting data on the use of biological agents in adult patients with systemic autoimmune diseases (SAD). The information source is a periodic surveillance of reported cases by a MEDLINE search (last update before this writing: December 31, 2007). The analysis included a total of 19 SAD and 6 biological agents. By December 31, 2007, the Registry included 1370 patients with SAD who had been treated with biological agents (562 received infliximab, 463 rituximab, 285 etanercept, 42 anakinra, and 18 adalimumab). SAD included Sjögren syndrome (SS; 215 cases), Wegener granulomatosis (261 cases), sarcoidosis (219 cases), systemic lupus erythematosus (SLE; 172 cases), Behçet disease (173 cases), adult-onset Still disease (118 cases), cryoglobulinemia (88 cases), and other diseases (80 cases). The higher rate of therapeutic response was found for the use of rituximab in patients with SLE (90%), SS (91%), antiphospholipid syndrome (92%), and cryoglobulinemia (87%); infliximab in sarcoidosis (99%), adult-onset Still disease (90%), and polychondritis (86%); and etanercept in Behçet disease (96%). Results from controlled trials showed lack of efficacy for the use of infliximab in SS and etanercept in SS, Wegener granulomatosis, and sarcoidosis. In addition, an excess of side effects (>50% of reported cases) was observed for the use of infliximab in inflammatory myopathies and sarcoidosis, and for the use of etanercept in polymyositis. Sufficient data are not yet available to evaluate fully the efficacy and safety of adalimumab and anakinra in patients with SAD. In conclusion, current scientific evidence on the use of biological therapies in patients with SAD is mainly based on uncontrolled, observational data. The best results have been observed in the use of rituximab for SS, SLE, and cryoglobulinemia; infliximab for sarcoidosis and adult-onset Still disease; and etanercept for Behçet disease. Lack of efficacy was demonstrated for infliximab and etanercept in SS, for etanercept in Wegener granulomatosis and sarcoidosis, and for anti-tumor necrosis factor (TNF) in SS. Future controlled trials are needed to confirm the potential use of biological therapies in patients with SAD.