The VI. International Workshop on Physics of Nonideal Plasmas (PNP VI) took place from November 18th to 21th, 1991, in Gosen (Germany) at the Science communication & Conference Centre of the Humboldt University of Berlin. The workshop was organized by the Institute for Theoretical Physics of the Humboldt University and by the Central Institute of Electron Physics, Berlin, with financial support given by the Deutsche Forschungsgemeinschaft, Bonn, and the Robert-Bosch-Stiftung, Stuttgart. The workshop was attended by more than 100 scientists from 14 countries who presented about 120 papers, including 18 invited lectures. The series of PNP workshops, which started in 1980, provides a biennial forum for both experimental and theoretical research in the field of nonideal plasmas. These meetings are organized alternately by the Central Institute of Electron Physics, Berlin, and/or by one of the universities of Berlin, Greifswald, and Rostock. They took place in Matzlow-Garwitz (1980), Wustrow (1982 and 1988), Biesenthal (1984), and Greifswald (1986). Since the beginning, the workshop has been concerned mainly with fundamental studies of the thermodynamic, transport, and radiative properties of nonideal plasmas. These fields were also covered at PNP VI in Gosen, but new topics such as high-pressure laser plasmas, dense astrophysical plasmas, molecular dynamics and Monte-Carlo results, and the kinetics of transitions have completed the programme. In particular, several papers addressed the role of nonideal plasmas for radiation sources, for inertial confinement fusion, for helio-seismology, and for the determination of the structure of the giant planets.