The aim of the present study was to determine the Hepatitis B Virus (HBV), Hepatitis C Virus (HCV), and diabetes mellitus (I)M) frequencies in lichen planus (LP) cases in our region. We performed a retrospective review of records from all cases that were diagnosed with LP at the our department between 1997 and 2002. The results were compared with the control group (an), type of dermatosis other than LP). The 260 LP cases included 108 (41.5%) males and 152 (58.5%) females aged between 5 and 78 years. The clinical distribution of the lesions were 127 (48.8%) with skin lesions and 133 (51.2%) with oral mucosal lesions. The duration of disease Fanged from I to 240 months. In 140 of 260 LP cases, hepatitis serology and pre-prandial blood glucose were examined. We found HBV positivity in 24 (17.1%) cases, Anti-HCV positivity in 7 (5%) cases, and DM in 22 (15.7%) cases. The control group included 116 (41.4%) males and 164 (58.6%) females. Their ages ranged between 10 and 82 years. In this group, we found HBV positivity in 20 (7.1%), And HCV positivity in 4 (1.4%), and DM in 20 (7.1%) cases. We believe that the co-association of LP with HCV is significant and this co-association ratio indicates variance depending on clinical attributes of the lesions and racial characteristics of the patients. Although we found co-associations between HBV and LP or DM and LP, we believe that further studies are necessary to determine if they are significant.