During the preparation oforganic, compost (150 days) five samples were taken of the arthropod fauna in each of three diferent treatments: fresh vegetable material alone (treatment 1); treatment 1 with chicken manure (treatment 2); and treatment 1 with residues of barley (treatment 3). All treatments were inoculated with bacteria after 75 days and all were covered by plastic sheetting for the greater part of the study period. In all of the three treatments, the most numerically important group was the Acari (88-99,5%) fallowed by Collembola (03-01%), Colleoptera (0,1-1,4%), Diplopoda (0,04-0,31%), Diptera (0,4-0,65%), and Formicidae. (0,01 -0,03%). The number individuals, and taxonomic groups, of the fauna increased gradually during the preparation of the compost, in all treatments. The bacterial inoculation at 75 days, produced an increase in the fauna in treatments I and 3, but not in treatment 2, moot likely because the chicken manure already had suffient microorganisms to ensure maximum degradation of the vegetable material. Covering the compost, heaps with plastic clearly decreased the number of arthropods. Uncovered compost treated with chicken manure has the highest taxonomic diversity of arthropods and the fastest rate of decomposition.