The Western Coast of Florida frequently experiences a harmful algalbloom caused by the dinoflagellate, Gymnodinium breve (G. Breve). G.Breve releases a toxin when the cells lyse, and this toxin becomes partof the marine aerosol. When humans are exposed to G. Breve toxin inmarine aerosol, upper respiratory symptoms such as runny nose, nasal congestion, cough, and sore throat are commonly reported. Since the estimated size of the particle is 7 - 10 mm most toxin should be filtered by the upper airway. If the lower airway is impacted by the red tide toxin, bronchoconstriction of the smooth muscle may occur. The common method to detect bronchoconstriction is the measurement of the Forced Vital Capacity (FVC) and the forced vital capacity exhaled in 1 second (FeV1). The purpose of this pilot study was to see if occupational exposure to red tide toxin during a scientific research cruise could be detected through spirometry. A spirometer providing hard copy of the flow volume loop was placed on three research cruises in 1998 and 1999. Data on the third research cruise is currently being collected. The primary purpose of these cruises was to conduct experiments in a red tide bloom in the Gulf of Mexico. Fifteen volunteer scientists were instructed on the correct method to perform the FVC maneuver. They were also asked to complete a Health History Questionnaire (Hollister Inc, 1980). The volunteers then performed a forced vital capacity maneuver at varying times of the cruises and also documented any respiratory symptoms. Variation in FVC and FeV1 in correlation to cell counts and aerosol collection will be discussed. This is an initial investigation of the occupational exposure to the red tide toxin in the marine aerosol.