Antinuclear antibodies (ANA) are often present in connective tissue diseases. In 279 non-selected patients with connective tissue disease, inflammatory and degenerative joint disease, in some patients with chronic infectious diseases and malignancies and in the presence of some unclear pathologic conditions in patients whose serum reacted positively to ANA, we analyzed the type of immunofluorescence and the presence of extractable antinuclear antibodies (ENA). In systemic lupus erythematosus, the prevailing immunofluorescence is type H (homogenous) (60.6%), anti-Ro/SS-A appears in 24.2%, anti-Sm and anti-RNP in 12.1%. In Sjögren's syndrome, type S prevails (47.6%), anti- Ro/SS-A and anti-La/SS-B are present in 52.4%, only anti-Ro/SS-A in 28.6%. In systemic sclerosis, the prevailing immunofluorescence is type S (37.5%), in 75% a positive anti-Scl-70 antibody is present. In mixed connective tissue disease, anti-RNP appears in 85.7%. In dermatopolymyositis, the anti-Jo-1 antibody is present in 33.3%. In undifferentiated connective tissue disease, type S immunofluorescence appears in 70%. In rheumatoid arthritis the prevailing immunofluorescence is type H (homogenous) (46.4%) and type S (speckled) (41.0%), while the presence of ENA is rare (anti-Ro/SS-A in 4.6%). In spondylarthritis, type S immunofluorescence appears most often (62.5%). Patients with chronic infectious disease, malignancies, undefined conditions and degenerative joint disease present with various types of immunofluorescence; the presence of ENA is extremely rare in these patients. The results of this study underline the significance of ANA and, particularly ENA, in the diagnosis of connective tissue disease. These antibodies however, can also be identified in various infectious and malignant diseases as well as in inflammatory and degenerative joint diseases.