To find predictors of outcome and to describe the long term outcome for children who require mechanical ventilation after nearly drowning. From 1981 to 1989, all children who underwent ventilation in the Intensive Care Unit of the Master Children's Hospital, Brisbane, after an immersion. Children who died within 24 hours were excluded. Of 57 children eligible for entry, 18 died after 24 hours. Retrospective study of hospital records and prospective assessment of neurodevelopmental outcome. Thirty-eight families of survivors were contacted by questionnaire and 25 children of these families were examined. Follow-up was between 0.8 and 9.6 years after immersion. All children who had a motor response to pain in the hospital's emergency department survived without sequelae. Thirty-one children were in cardiac arrest and, of these, 17 died, six survived with severe spastic quadriplegia and eight are ambulant. Of those ambulant, four have motor coordination difficulties and three have learning difficulties. Children in cardiac arrest who had a delay of more than 20 minutes between rescue and arrival at hospital were more likely to die or sustain severe spastic quadriplegia. No child survived if more than 25 minutes of advanced resuscitation was required after they had been warmed. Children with a motor response to pain seem to have a good prognosis. However, we could not predict which children in cardiac arrest would die or survive either severely impaired or ambulant. All children in cardiac arrest should receive aggressive resuscitation for at least 25 minutes after being warmed; they have a better prognosis if advanced resuscitation is started less than 20 minutes after rescue. Children who survive a cardiac arrest without spastic quadriplegia warrant long term surveillance as they may have coordination and learning difficulties.