From January 1984 to May 1994, 17 of 239 children under 15 years old stung by Tityus serrulatus (15.1%) or Tityus bahiensis (84.9%) presented severe envenoming. Of these 17 patients (1-11 years old; median = 2 yr) 14 were stung by T. serrulatus and three by T. bahiensis. All of them received scorpion antivenom i.v. at times ranging from 45 min. to 5 h after the accident (median = 2 h). On admission, the main clinical manifestations and laboratory and electrocardiographic changes were: vomiting (17), diaphoresis (15), tachycardia (14), prostration (10), tachypnea (8), arterial hypertension (7), arterial hypotension (5), tremors (5), hypothermia (4), hyperglycemia (17), leukocytosis (16/16), hypokalemia (13/17), increased CK-MB enzyme activity (> 6% of the total CK, 11/12), hyperamylasemia (11/14), sinusal tachycardia (16/17) and a myocardial infarction-like pattern (11/17). Six patients stung by T. serrulatus had depressed left ventricular systolic function assessed by means of echocardiography. Of these, five presented pulmonary edema and four had shock. A child aged two-years old presented severe respiratory failure and died 65 h after being stung by T. serrulatus. Severe envenomations caused by T. serrulatus were 26.2 times more frequent than those caused by T. bahiensis (p < 0.001).