For a period of 8 days, pregnant white New Zealand rabbits were treated either with the beta-sympathomimetic Ritodrine (1 mg/kg) body weight daily) or with 0.9% saline solution. The fetuses were delivered by caesarian section on the 25th and 30th day of gestation (term being 31 days). No significant difference was found between the Ritodrine and saline treated groups with respect to the levels of dipalmitoyl-lecithin (DPL) obtained from the homogenates as well as the alveolar lavages of the fetal lungs. These results indicate that with this experimental model, prepartum treatment with Ritodrine has no effect either on DPL synthesis or its release into the alveolar spaces. Furthermore, treatment with the beta-sympathomimetic produced no significant change in the concentrations of the specific glucocorticoid receptors in the cytosol and nuclei of the fetal lungs, and in addition, the lung cytosol glucose concentrations as well as the plasma corticosteroid levels were unaffected. These findings support the conclusion that the synthesis of DPL in the fetal lung is not stimulated by Ritodrine.