A program aimed at making measurements principally of biological particles (pollen, spores, bacteria) at the ground and aloft over an extended grassland region, was performed in the neighborhood of Miles City, Montana, during the period of operation of Project CCOPE a large multiinstitutional field study of the characteristics of convective storms. Project CCOPE offered a large framework of measurements of atmospheric parameters useful for the interpretation of measured concentrations of biological particles and their behavior in height and time. The measurements carried out are being studied in relation to air trajectories, air mass changes, and the known distribution of sources of detected particles. Analysis of filter samples performed between ground level and 6000 m height revealed significant concentrations of biological particles at all heights, and some interesting observations of transport of non-biological particles emitted by a coal-fired power plant to at least 6000 m. Some meteorological explanations of the observations are offered.