Outbred male and female Wistar rats demonstrated large and consistent interindividual variations in nocturnal blood ethanol level (BEL) during ad lib access to food, water and an ethanol solution. Mean individual BEL ranged from 0--109 mg/dl, grand mean = 25.1 mg/dl (5.5 mM). BELs of all rats correlated with free-choice ethanol intakes, but females showed significantly greater ethanol intake (female and male means = 10.5 and 8.2 g/kg/24 hr) that was unaccompanied by significantly greater BEL (female and male means = 30.6 and 19.6 mg/dl). Across three linearly derived generations, progeny of rats matched for high BELs (mean = 25.1 mg/dl), but there was no significant difference across generations in ethanol intake (respective means = 8.4 and 8.1 g/kg/24 hr). In the third derived generation, there were significant differences between high and low BEL progeny in both BEL (respective means = 35 and 15 mg/dl) and ethanol intake (respective means = 8.2 and 6.3 g/kg/24 hr).