The levels of 3-methoxy-4-hydroxy ethyleneglycol, MOPEG, the main metabolite of noradrenaline in the CNS, were determined in lumbar cerebrospinal fluid of healthy male volunteers. The subjects had been alcohol-free for at least one week and were investigated after intake of 60, 80 or 120 g of ethanol. One week before or after the experiment control samples were obtained. All subjects showed increased MOPEG levels during intoxication, and the MOPEG elevation was significantly correlated to blood ethanol concentration. During control conditions MOPEG levels were fairly constant over time but there were higher levels at night than in the morning. The baseline levels of MOPEG were negatively correlated to the reported habitual alcohol intake of the subjects, and also to the occurrence of dependency traits in their drinking pattern. Subjects with first-degree relatives with alcohol problems had lower MOPEG levels than the rest. Assuming that changes of MOPEG levels in cerebrospinal fluid are dependent on changes of central nervous system noradrenaline turnover, the results indicate that alcohol intoxication is related to a central noradrenergic stimulation, and that the activity of central noradrenaline systems is of importance for longterm alcohol habits in man.