Plasma DBH activity levels were determined for 22 nonalcoholic young men with alcoholic close relatives (the FHP or family history positive group) and results compared to family history negative (FHN) controls matched on demography, height/weight ratio, and drinking history. These enzyme levels were then correlated with the usual drinking history over the prior 6 months and with the intensity of intoxication achieved after drinking 0.75 ml of ethanol/kg body weight. The FHP men demonstrated a 20% lower level of DBH (p greater than 0.1) indicating no significant difference between the groups. Base-line DBH activities correlated significantly with the level of intoxication for the FHN group (r = 0.44, p less than 0.025) with a trend for an inverse correlation with the average drinking history. FHP men, on the other hand, demonstrated only a nonsignificant association between peak intoxication level and base-line DBH and a positive correlation (r = 0.37, p less than 0.05) with the average number of drinks/drinking day. These results are not consistent with the probability that a premorbid DBH assay could be used as one indicator of propensity towards alcoholism. The differences between FHP and FHN groups on correlations between DBH and peak intoxication or usual drinking history raise speculations that the "normal" (FHN) relationship between alcohol intake and plasma DBH activity may be impaired in individuals at high risk (FHP) for the future development of alcoholism.