In the future, there is a potential for anthropogenic microbial air pollution (MAP) associated with large-scale use of microbial pesticides and other microbials in forestry and agriculture, and other agricultural practices and urban activities, particularly sewage treatment and solid waste composting. If we are to manage the atmospheric bacterial loading from these sources, we must have a better understanding of the dynamics of airborne bacterial populations. The report describes a first step in understanding these dynamics by evaluating the flux of bacteria during daylight hours at an isolated location in the high desert chaparral. The idea here is to use the flux of bacteria from natural sources as a surrogate for micro-organisms applied to vegetation by man.