Connective tissue diseases (CTDs) are multisystem autoimmune disorders with a chronic relapsing and remitting course. Due to the absence of definitive diagnostic tests, their diagnosis essentially relies on evolving classification criteria. Undifferentiated CTD (UCTD) and overlap syndromes frequently present with overlapping features of well defined CTDs, while mixed connective tissue disease (MCTD) is a distinct entity. Although a number of UCTD cases may never progress into a defined CTD, early progression, usually within 5 years, is common. Management is based on symptoms, severity of organ involvement, and treatment protocols of the primary CTDs. Pulmonary hypertension is one of the leading causes of mortality in MCTD, while complications such as Raynaud’s phenomenon, ILD, and hematologic and renal involvement also contribute to morbidity and mortality. In CTDs, regular monitoring for disease progression and disease as well as treatment-related complications is essential. Prognosis of overlap CTDs is usually better than primary forms, especially in patients with high U1-RNP antibodies. The goals of therapy should be symptom control, prevention and control organ damage, and reduction of treatment-related side effects.