There are many different species of the Loxosceles throughout the continental United States. Several of these have been reported to cause arachnidism similar to that of the L reclusa, the brown spider. Thirty-three patients had L reclusa spider bites. Hospitalization and nonoperative treatment (11 cases), late incision (15 cases), and early excision (seven cases) led us to the conclusion that early excision of lesions greater than 1 cm is the best treatment. Early symptoms from the bite may be minor and delayed or occur within a few hours and be severe. Necrosis taking several weeks to heal is common. The bites are arranged in four categories of severity. A specific test for loxoscelism with radioactive thymidine is available, but anyone bitten by a spider should capture it and bring it with him to the physician.