Objective of the study was the evaluation of microbial and endotoxin immissions in an area surrounding a composting plant. Immissions of microorganisms and endotoxin originating from a composting plant working with the Herhof boxsystem were measured. Samples were collected in the vicinity of the plant with filter samplers using gelatin filters (MD 8 of Sartorius). Total aerobic bacteria, staphylococci, coliforms and total Gram-negative bacteria were recorded. Mesophilic fungi were investigated using two different media: DG 18 agar and malt extract agar with two temperatures (22°C and 30°C). Aspergillus fumigatus was scored incubation temperature of 45°C. Measured airborne used to calculate the emission rate expressed as cfu per h by employing a dispersal model according to the German TA Luft, Annex C or a modified formula for emission from chimneys. Immissions in the area surrounding the plant were recalculated using these models. As a result of these calculations no significant increase of microbial concentration compared to the concentrations described in literature for ambient air could be predicted at a distance of more than 500 m under the conditions employed. This indicates that composting facilities of the investigated type do not initiate heavy immissions in their vicinities. Only very small endotoxin concentrations could be detected outside the composting plant.