To study the effects of maternal alcohol ingestion on brain adenylate cyclase in offspring, rats were given ethanol in the drinking water before, during and after gestation. Fifteen-day-old pups from alcoholic mothers had reduced body and wet brain weight and protein content with normal concentrations of DNA and RNA in brain; pups from mothers deprived of alcohol from the 21st day of gestation had normal growth and brain protein, DNA, RNA and cyclic nucleotide concentrations. Adenylate cyclase activity was less in homogenates from the diencephalon, mesencephalon and cerebellum of alcoholic and alcohol-deprived mothers than in the corresponding homogenates from control mothers. A reduction of the enzyme activity was only observed in homogenates from diencephalon of offspring from alcoholic and alcohol-deprived mothers as compared with controls. Sensitivity of adenylate cyclase to noradrenaline was reduced in the corpora striata and diencephalon from alcoholic mothers, while these changes were absent in alcohol-deprived mothers and their offspring. Ingestion of ethanol in pregnant mothers does not seem to affect significantly the adenylate system in the brain of the offspring.