The clinical picture as well as the principles of treatment in ethylene glycol poisoning differ with the time after ingestion. These time-related differences are illustrated by two case reports. During the first hours of ethylene glycol poisoning, the patient suffers from drunkenness, vomiting and somnolence due to the intoxicant effect of ethylene glycol on the central nervous system. In the following hours a poisoning with glycolate and oxalate develops, with increasing acidosis, renal and brain damage. A patient admitted within a few hours of an overdose, with no or only slight metabolic acidosis, may be successfully treated with ethanol. If the serum concentration of ethylene glycol is very high, hemodialysis may be deferred until the necessary staff and equipment are available. If the patient is admitted with severe metabolic acidosis, hemodialysis must be started immediately. The need for ethanol administration during hemodialysis merits reevaluation.