Geoscientific modelling has some unique requirements. Modern geological applications require increasingly quantitative and accurate rock property characerizations within the three-dimensional subsurface environment. this problem differs from that faced by most other fields due to a variety of technocal and economic constriants. Three-dimensional geoscientific modelling often relies on complex stochastic concepts and thus requires the extraction of information from large multiparameter data sets, and the representation and modification of complex, and uncertain geo-objects of interest. The visualization of these three-dimensional features has been a major constraint. The ability to rapidly create and manipulate three-dimensional imgages can materially speed up the geoscientist's understanding of the subsurface environment. The wok is organized arou d four major themes: definition of the problem; description of existing 3-D geoscientific information systems; 3-D data structures and display methods; and applications of 3-D geoscientific modelling. The contributors are drawn from most of the NATO nations, Sweden and Japan, representing national geological surveys, the petroleum, mining, environmental and engineering industries, universities and computer hardware and software companies.