An epidemiological and clinical study of Parabuthus transvaalicus scorpionism was conducted in Zimbabwe. Ten per cent of stings resulted in severe scorpionism. The clinical features of 17 patients with severe envenomation were primarily neuromuscular, with significant parasympathetic nervous system and cardiac involvement. The clinical course was prolonged compared to other scorpion syndromes, and significant therapeutic benefit was demonstrated in terms of hospital stay in response to species specific antivenom. The case fatality rate was 0.3%, with deaths in children below 10 years and adults above 50 years. The mortality rate in the district was 2.8 per 100,000 per year. This syndrome from a buthid scorpion resembles in many respects buthid scorpionism described elsewhere in the world, but shows important differences, notably cardiac involvement in the absence of clinical evidence of circulating catecholamines. The relevance of these findings to buthid scorpionism generally are presented as a hypothesis, in which it is postulated that the cardiac effects of the toxins are direct and primary, and autonomic effects secondary but synergistic, determining the ultimate clinical picture.