In our view, the First International Penicillium and Aspergillus Workshop held in Baarn and Amsterdam in May, 1985, was a great success. The assembly in one place of so many specialists in these two genera produced both interesting viewpoints and lively discussions. But more particularly, a remarkable cohesion of ideas emerged, borne primarily of the realisation that taxonomy has passed from the hands of the solitary morphologist. The future of taxonomy lay in collaborative and multidisciplinary studies embracing morphology, physiology and newer methodologies. Penicillium and Aspergillus Workshop was borne logically The Second International from the first, and was held in Baarn on May 8-12, 1989. It was attended by 38 scientists from 16 countries. At this Workshop we have attempted to move further into new methods, especially by bringing together molecular biologists, medical and food mycologists and biochemists as well as more traditional taxonomists. We feel that the meeting contributed greatly to dialogue between taxonomists, and also fundamental and applied mycologists. At the meeting, we became aware that the approach to taxonomy of these genera is now becoming more pragmatic, with an increasing emphasis on consensus, and on stability of names. This is a noteworthy development, which we, as editors, welcome. So many species in Penicillium and Aspergillus are economically important in biotechnology, foods and medicine, and practical, stable taxonomy is of vital importance. These Proceedings comprise 40 papers divided into 9 chapters.