Background: Collett's snake (Pseudechis colletti) is a member of the black snake genus and occurs in a warm temperate to sub-tropical region of central Queensland, Australia. There are no reports of bites occurring in the wild, and bites were previously thought to cause only minor effects. They are a popular snake among zoos and exotic snake keepers.Aim: To investigate the clinical effects of severe envenoming by Collett's snake, and possible treatment options.Design: Case series.Methods: Clinical and laboratory features are described for six bites, all in snake handlers.Results: All six bites were from captive snakes, resulting in severe envenoming in four. Two patients were treated early with black snake antivenom, and only developed an anticoagulant coagulopathy and mild myolysis. Two developed anticoagulant coagulopathy and severe rhabdomyolysis associated with acute renal failure, requiring haemodialysis; both received antivenom > 10 h after the bite, and initially received minimal fluid replacement. Other effects included thrombocytopenia, non-immune haemolytic anaemia and a marked leukocytosis.Discussion: Collett's snake envenoming is characterized by early generalized systemic effects (nausea, vomiting, abdominal pain, diarrhoea and headache) and an anticoagulant coagulopathy, followed in some cases by rhabdomyolysis and acute renal failure in untreated patients within 24 h. Early initiation of fluid therapy and treatment with black snake antivenom should be undertaken in all envenomed patients.