Multisystem autoimmune rheumatic diseases are heterogeneous rare disorders associated with substantial morbidity and mortality. Efforts to create international consensus within the past decade have resulted in the publication of new classification or nomenclature criteria for several autoimmune rheumatic diseases, specifically for systemic lupus erythematosus, Sjögren's syndrome, and the systemic vasculitides. Substantial progress has been made in the formulation of new criteria in systemic sclerosis and idiopathic infl ammatory myositis. Although the autoimmune rheumatic diseases share many common features and clinical presentations, diff erentiation between the diseases is crucial because of important distinctions in clinical course, appropriate drugs, and prognoses. We review some of the dilemmas in the diagnosis of these autoimmune rheumatic diseases, and focus on the importance of new classification criteria, clinical assessment, and interpretation of autoimmune serology. In this era of improvement of mortality rates for patients with autoimmune rheumatic diseases, we pay particular attention to the effect of leading complications, specifi cally cardiovascular manifestations and cancer, and we update epidemiology and prognosis.