The only spiders of real medical importance to humans in the United States are the Loxosceles and Latrodectus species, primarily the brown recluse and the black window, respectively. These spiders bite humans only when trapped or crushed against the skin. Severe brown recluse spider bites produce dermonecrosis within 72-96 hours, which should be treated with rest, ice compresses, antibiotics, dapsone, and surgery delayed for several weeks. Using systemic corticosteroids may be helpful in treating the much rarer systemic loxoscelism, which has minimal skin changes but produces massive hemolysis. Black widow bites do not produce marked skin changes but primarily produce muscle cramping, pain, and other neuromuscular-related symptoms. Though a specific antivenin for black widow bites is available, pain control, muscle relaxants, and calcium gluconate are generally adequate treatment. Many other spiders inflict painful bites, but arachnids do not medically deserve the bad reputation that they generally have with the public.