A preliminary screen was conducted at six sites to characterize sludge with regard to bacterial and viral microorganisms, trace metals, organoechlorine pesticides, and PCB's, and to evaluate each site for its suitability for aerosol monitoring. Four sites were selected for aerosol monitoring, two practicing tank truck application and two practicing spray gun application. From five to eight aerosol monitoring runs were made at each of the four sites, and a special enterovirus aerosol run was conducted at one of the spray sites. The preliminary screens were used to indicate what levels of microbiological and chemical constituents could be routinely expected in liquid sludge. The aerosol data were used to indicate whether there was aerosolization of microbiological constituents and as input to dispersion modeling. There was some evidence of aerosolization at the tank truck sites and strong evidence at the spray sites, particularly in the fecal coliform and fecal streptococci data. Modeling of the results proved difficult and there is considerable uncertainty in the data presented. No human enteric viruses were detected on the special run, which translates into a concentration of less than 0.0016 pfu/m3 at a distance of 40 m downwind from the spray gun. The inability to detect viruses in the air most likely resulted from the low concentration in the sludge and from their adsorption into the solid matter in the sludge which is not easily aerosolized.