Erythema Multiforme (EM) is a type of allergic reaction that occurs in response to medications, infections, or different illnesses. In many cases, a definite underlying cause may not be identified. This study aimed to evaluate adult EM outpatients with regard to patients characteristics, the disease and the underlying contributors. In this cross-sectional study, 61 adult EA outpatients referred to the Dermatology Clinic of Tabriz Sina Hospital were recruited during a 12-month period (January 2009-January 2010). The diagnosis was made based on clinical and morphologic grounds. Age, sex, types of EA, location and type of the lesions and the underlying causes were documents. An infectious etiology was suspected when a preceding illness was noticed without drug ingestion within 1 week prior to the onset of the rash. A drug related to the condition was defined as every drug that has been taken during 21 days prior to the onset of any symptoms. There were 34 males and 27 females with a mean age of 26.8±15.3 (18-57) years enrolled. The EM was minor in 62.3% and major in 37.7% of patients. The upper limb was involved in all patients. The lesions were maculo-papular, vesiculobullous and bullous in 83.6, 13.1 and 3.3% cases, respectively. Drugs and herpes simplex were the main causes in 49.2 and 16.4% of patients, respectively. The disease was idiopathic in 34.4%. The underlying drugs were sulfonamides in 12 cases (19.7%), penicillin in 5 cases (8.2%), salicylic acid, aspirin, cimetidine and amoxicillin each one in 3 cases (4.9%) and barbiturate in 1 case (1.6%). Five cases (8.2%) were recurrent EM including 4 males and 1 female, 3 idiopathic and 2 cases due to sulfonamides.