Latrodectism-envenomation by the black widow spider, Latrodectus mactans-has been reported in virtually every state. The spider is particularly prevalent in the Southwest, Southeast and California, and symptoms from its bite are painful and may be confusing to clinicians. Prompt improvement can be expected in most cases with administration of calcium and muscle relaxant, but some patients may require treatment with antivenin. No deaths occurred in our series of 11 patients, although one case was complicated by serum sickness.