Ten patients with CF who were more than 18 years old, participated in a double-blind, placebo-controlled study evaluating the efficacy of inhaled ipratropium bromide and metaproterenol as bronchodilators. The mean FEV1 of the group improved 17.1 percent after treatment with ipratropium bromide, 12.5 percent after metaproterenol treatment, and 16.6 percent after treatment with both of these medications together. There was no significant difference between these responses and patients who respond to one treatment tended to respond to the others. The side effects with these medications were minimal. When compared with patients in previous studies, our patients, who were much older as a group, demonstrated a greater degree of bronchodilation with ipratropium bromide and metaproterenol, as well as a greater degree of bronchoconstriction with placebo.