OUTLINE: This is a randomized, double-blind, placebo-controlled, cross-over, multicenter study. Patients are randomized to one of two arms, then cross-over to the other arm. Arm I: Patients receive INS316 by inhalation via a nebulizer. Sputum is collected throughout the dosing and for 1 hour post dosing. Arm II: Patients receive placebo in the same manner as INS136 in arm I. All patients receive both treatments. Patients receive the first dose no more than 7 days after screening, and the second dose 3 to 10 days after the first dose. Patients are followed 1 day after completion of the second treatment. The sputum samples are fixed and examined cytologically.