This paper reports a case of loxoscelism associated with reversible right hemidiaphragmatic paralysis. The diagnosis of loxoscelism was based upon the description of the spider by the patient himself and by the typical clinical findings which included necrosis at the site of the bite with a scarlet fever-like skin rash, intravascular hemolysis, hemoglobinuria, coagulation disturbances and acute renal failure. The treatment was supportive with full recovery of these abnormalities. The diagnosis of diaphragmatic paralysis was based upon the elevation of the right hemidiaphragm in a full inspired film 5,8 cm above the left hemidiaphragm and in its imobility detected through a radioscopic examination. A chest x-ray film taken before the envenomation did not show any sign of diafragm paralysis as did another chest x-ray film taken one month after the spider bite. These findings lead to suspect the diaphragmatic paralysis to be related to the venom action or to another systemic complication of loxoscelism.