AbstractIn order to investigate the effect of different polluting agents to fungi, there is an obvious need for methods for estimating fungal growth. Given that the traditional methods are not accurate and efficient enough, the aim of this work has been to establish new and better ones. The main emphasis has been on a method based on growth in liquid solutions, in which increase in hyphal biomass is registrated optically. Complying with the results of other workers, this methodology is shown to provide information about how metal ions influence fungal growth. This part of the work suggests four toxicity groups. Also in this thesis I present a method for fungal growth studies that enable the investigator to work on a microscopic level. By letting the myceliumgrow in a layer with the thickness of only one cell on a microscope slide, both growth distance and cell morphology can be scrutinized through microscope techniques.Finally I put forward a technique for continually investigating the effect of toxic agents on hyphal growth during several weeks. Here the growth proceeds in the wall of a hollow agarose sylindar, protected by a glasstube. The growth is kept pace with by a mechanical typewriter, modified to transfer growth distance from the growth tube to a sheet of paper. All experiments have been conducted upon mycelia from the Alpine basidiomycete Lepista multiforme (Romell) Gulden.