Inhalation of pharmacologically active substances for medicinal, social, or recreational purposes has been prevalent for centuries but experience of exploiting the lung as a route of delivery for treatment of nonrespiratory diseases is limited. Despite the success of current applications such as anesthetics, the utility of the lung for drug delivery is not well appreciated, despite advantages such as rapid onset of action. Two drawbacks are the relatively poor efficiency of current inhalation devices, especially for large molecules, and the poor patient acceptability of inhalers. Advances now being made in pulmonary delivery technology may provide the impetus needed for the development of new inhaled presentations of drugs such as peptide hormones and other biologically derived molecules. Molecules of various sizes can be delivered in clinically relevant quantities via the lung. In vitro methods show that lipophilic drugs are absorbed through the alveolar membrane more quickly. Early work in animal models has already shown that absorption of analgesic and antiinflammatory drugs that are not well absorbed orally can be improved by delivering them by inhalation. This work may soon give rise to new formulations for therapeutic use.