A considerable interest has been focused on the effects of various drugs on fetal and neonatal pulmonary maturation and adaptation. In the present study, we have investigated the effects of the selective beta1- and beta2-receptor-stimulating agents prenalterol and terbutalilne on the pressure-volume relationship and fluid content in fetal rabbit lung at 28 days of gestation. Pressure-volume recordings during deflation showed significantly increased lung volumes at equivalent transpulmonary pressures in terbutaline-treated fetuses as compared to controls. No such effect was noted after prenalterol. In the control animals, wet lung weight/body weight ratio decreased to a steady state level 60 min after birth, indicating a rapid dehydration of the lungs. This dehydration was present at delivery after terbutaline and prenalterol treatment. The amount of fluid collected from the airways was also reduced after terbutaline and prenalterol treatment. The present results indicate facilitated neonatal respiratory adaptation after especially terbutaline treatment. Possible mechanisms behind these effects are discussed.