Erythema nodosum refers to the development of multiple painful nodules in recurrent crops, commonly on the shins. Sixty percent of cases are idiopathic (without apparent cause). In the other forty percent, the skin lesions are simply the cutaneous manifestations of a systemic disease. Other diseases that are associated with erythema nodosum depend on the geographical location of the patient. In the Midwest, streptococcal infections predominate. In Scandinavia, tuberculosis is a consideration. In the Philippines, leprosy may be likely. In the Southwest of Unites States, coccidiomycosis is likely and in the Southeast, North American blastomycosis is likely. Drug eruptions to iodides, bromides, penicillin, sulfa drugs and birth control pills may be associated with erythema nodosum. This is an important disease to recognize and with appropriate therapy, the problem clears quickly.