The Triangulated Irregular Network (TIN) data format is directly applicable to modeling mountainous landscapes. For example, mountain cartographers may want to symbolize the TIN surface based on elevation changes or they can shade the facets of the TIN based on slope or aspect. During this presentation I will compare the functionality of building TINs using ArcGIS's ArcToolbox to the functionality in classic ArcInfo Workstation. ArcInfo provides a powerful suite of tools for creating TINs from a plethora of data formats. The formats include, point coverages, line coverages, polygon coverages, ASCII files, and GRID datasets. I will discuss how to process these various formats. I will detail special considerations when building TINs from mass points and breaklines. In addition, I will discuss the issues to consider when building TIN's from contour data. I will use real world examples from various terrains to illustrate these concepts. Users can then choose the most appropriate tools for their projects.