Autoantibodies are immunglobulins occurred directly against autoantigens that are known as endogen antigens. Autoimmune disease is an occasion that the body begins a fight against its own cells and tissues. The antibodies that are created by the body against its own cell nuclei are called as anti-nuclear antibodies (ANA), and one of the methods used for detection and pattern of ANA is indirect immunofluorescence test (IIF). In the present study, it was aimed to determine the rate of ANA positivity and patterns of the positive specimens, and to investigate the relationship between ANA positivity and diseases in patients.ANA test results of a total of 3127 patients admitted during March 2010 to December 2012 were evaluated retrospectively. ANA test (HEp 20-10, EUROIMMUN, Germany) was used in dilution of 1:100 in IIF test.A total of 494 (15.8%) resulted as ANA positive. ANA positivity rate was significantly higher in female patients than the male ones (p<0.001). The most frequent ANA patterns were coarse speckled pattern (154 patients, 31.2%), nucleolar pattern (89 patients, 18.0%), fine speckled pattern (57 patients, 11.5%), and speckled pattern (48 patients, 9.7%). ANA positivity was most commonly determined in rheumatoid arthritis (RA) (42 patients, 8.5%), systemic lupus erythematosus (SLE) (29 patients, 5.9%), and rheumatoid vasculitis (RV) (28 patients, 5.7%). The most frequent symptoms or findings were joint pain (127 patients, 26.0%) and anemia (28 patients, 5.7%). ANA positivity rates were found to be significantly higher in patients with RA (p<0.001), with SLE (p<0.001), and with Raynaud phenomenon (p=0.001) in comparison to the controls. Amongst the most frequent diseases evaluated, no significant differences were found between the control groups and the groups of RV (p=0.089), multiple sclerosis (p=0.374), and Sjögren syndrome (p=0.311) in terms of ANA positivity rates.The present study is the first study reporting the positivity rate and distribution of ANA in Bolu located in northwestern Turkey. Information about the pattern types and the distribution of the patterns according to the diseases and symptoms contribute in diagnosis of autoimmune diseases. It is observed that clinical diagnosis has been supported significantly by ANA test according to data of our study.