The suppressive effects of ethanol (EtOH) on the male rodent reproductive axis, especially on serum luteinizing hormone (LH) levels, are well known. In this study we examined, in coordinate fashion, the effects of EtOH on LH secretion and on steady-state levels of the mRNA for the two genes that direct LH synthesis, namely alpha- and beta-LH. A single intraperitoneal (IP) injection of EtOH given to castrated male rats produced a statistically significant fall in serum LH levels at 1.5 (p less than 0.05) and 3 hours (p less than 0.01) after injection compared to saline-injected controls. This effect had dissipated by 24 and 72 hours after treatment. Intrapituitary LH content was significantly increased in EtOH-compared to saline-treated animals 1.5 hours after injection (p less than 0.05) at the same time there was a significant decrease in serum LH. Steady-state levels of beta-LH mRNA were significantly diminished in EtOH-treated animals at 1.5 (p less than 0.05) and 3 hours (p less than 0.001) after injection, but returned to control levels thereafter. Since the half-life of beta-LH mRNA is greater than 8 hours, this fall is most likely due to decreased beta-LH mRNA stability and may also involve decreased beta-LH gene transcription. alpha mRNA levels were unchanged at all time points investigated. These findings were verified in four repetitions of this experiment. These data suggest that the EtOH-induced fall in serum LH is due to impaired secretion of LH and to decreased LH synthesis as indicated by diminished steady-state levels of beta-LH subunit mRNA, secondary mainly to altered mRNA stability.