A syndrome ascribed to neuroleptics. The syndrome includes hyperpyrexia (temperature over 39 degrees Celsius), autonomic instability and muscular rigidity. The syndrom is not dose related and appears to be related to a very wide variety of substances including antidepressants, antipsychotics and lithium. There is a significant risk of mortality. Whether the syndrome is a variant of the lethal catatonia syndrome (described before the advent of modern neuroleptics) is a debated point.