The aim of this retrospective study was to investigate whether plasma potassium, pH and activated clotting time (ACT), obtained from a central venous blood sample immediately after admission to hospital, could predict outcome in patients with severe accidental hypothermia and cardiocirculatory arrest. Twenty-two patients rewarmed with cardiopulmonary bypass were studied retrospectively (12 patients after avalanche accidents, seven patients after cold water submersion and three patients after prolonged exposure to cold). In 12 patients stable spontaneous circulation could not be restored. In 10 patients stable spontaneous circulation could be restored. Two of these 10 patients survived long-term. Plasma potassium, central venous pH and ACT were clinically useful prognostic markers in hypothermic arrest victims after avalanche accidents: a plasma potassium value exceeding 9 mmol/l, a pH equal to or less than 6.50 or an ACT exceeding 400 s was seen in patients in whom spontaneous circulation could not be restored. Plasma potassium, central venous pH and ACT were of only limited prognostic value in hypothermic arrest victims following cold water submersion or prolonged exposure to cold. In hypothermic arrest victims after cold water submersion a central venous pH as low as 6.51 on admission did not exclude long-term survival. Moderate and severe hyperkalemia in arrest victims after prolonged exposure to cold need not necessarily indicate postmortem autolysis. A decision to continue or terminate resuscitation cannot be based on laboratory parameters. Nevertheless, our data suggest that plasma potassium, central venous pH and ACT on admission can be used to identify hypothermic arrest victims in whom death preceded cooling. If several hypothermic arrest victims are admitted simultaneously after avalanche accidents, these 3 parameters can help not to waste limited cardiopulmonary bypass facilities for patients with no hope of survival.