The diagnosis of bite by the brown recluse spider, Loxosceles reclusus, is rarely based on absolute identification of the insect because the victims are usually bitten while sleeping or dressing. More often, the history, clinical findings and course of the bite lead to the diagnosis. For early confirmation up to 24 hours after the bite, the passive hemagglutination test can be used. For older lesions, the in-vitro lymphocyte transformation test is useful, but is available in only a few medical centers. Treatment of the bite of the brown recluse spider varies from conservative to more active approaches. Resting, local cooling, systemic antibiotics to prevent infection and mild anti-inflammatory drugs may be given. In the more active approach oral corticosteroids are added in the first 72 hours to the antibiotics, especially in massive bites with necrotic centers greater than 2 cm in diameter, or when there is systemic loxoscelism. Recently, good results have been reported with Avlosulfon (dapsone), which is claimed to cure necrotic cutaneous ulcerations, presumably by reducing the activity of polymorphonuclear leukocytes. Other treatments include specific antivenin, (of limited use because it must be administered shortly after the bite), and surgery to prevent spreading of the venom. We describe 3 cases of brown spider bite with typical clinical presentations in adults aged 20-40 years. 2 were treated with corticosteroids and antibiotics and 1 with Avlosulfon and prednisone, all within 72 hours of the bite. 2 recovered completely within a few days, but the third treated with prednisone and antibiotics, developed an ulcer which healed only after several months of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)