Bachground: Erythroderma is a rare but serious skin disorder that may result from different causes. There are many publications on this subject, with a different incidence rate for each etiology. The aim of this study was to determine the frequency of erythroderma, and describe the incidence of each etiologic cause in patients indigenous to Khuzestan. Methods: In a retrospective study, we reviewed the files of patients diagnosed with erythroderma who were admitted to the dermatology ward of Sina Hospital, affiliated to Jondishapour Medical University of Ahvaz, southwest of Iran, in a period of 9 years from 1980 to 1989. We studied the clinical and pathology reports of patients and the final etiologic diagnosis. Results: Total admission was 6210 patients and the total number of erythrodermic patients was 85. The frequency of erythroderma in our dermatology department was 1.37%. The most common causes in order of frequency were eczema (32.94%), drug reaction (23.52%), psoriasis (21/18%), and malignancy (8.23%). Previous history of skin disease was found in 44 of 85 patients (51.76%) and 28 (32.9%) of them were suffering from eczema. The mean age of our patients was 49.11 years and the male-female ratio was 1.6:1. Conclusion: Erythroderma is a rare condition. The most common causes in our study were eczema and drug reactions; the high incidence of drug reactions in our patients compared to studies in other countries may be due to more administration of drugs in Iran, especially in Khuzestan.