The clubroot disease of the Brassicaceae, caused by the obligate biotroph Plasmodiophora brassicae, is one of the most damaging diseases within this plant family. Despite the fact that P brassicae was identified as the causal agent of the clubroot disease already in the last century, its life cycle is still not entirely clear. The employment of molecular techniques to clubroot research has provided new means to identify the fungus more easily in plane tissues and has led to the identification of several factors important for the host-pathogen interaction The use of mutants and transgenic plants of Arabidopsis thaliana have advanced the understanding towards the processes leading to successful invasion of the host as well as to resistance mechanisms. The possibilities of increasing tolerance/resistance to P. brassicae are described and discussed. These results should be also beneficial to agricultural applications.