Since 1997 the Reinhaltungsverband Leoben has been running a sewage sludge composting plant. With the coming into force of the 2001 ministerial order for compost, new limit values must be complied with. This holds true for particularly nickel, cadmium and mercury, which in sewage sludge compost are sometimes present in excess. The aim of this study was to examine the magnetic properties of organic waste, sewage sludge and compost of the sewage plant Leoben and to determine on the basis of chemical analyses the magnetic parameters which are especially suited to indicate heavy metals in Leoben and its surroundings. Magnetic characterizations of the mineral phases were carried out on selected samples. Moreover, additional mineralogical examinations were performed by way of reflected-light microscopy, scanning electron microscopy and microprobing to analyse the mineral composition. The findings of the investigations proved that the magnetic fraction of the individual samples virtually consists solely of anthropogenic particles. A comparison of the magnetic parameters with the heavy metal content further showed a significant positive correlation with arsenic, cadmium, chrome, cobalt, lead and the like. The achieved results confirm that magnetic analysis provides (in combination with mineralogical analyses) significant results in the steel and iron manufacturing industry, for example in Leoben, with respect to both type as well as amount of anthropogenic particles.