The authors describe methods for classifying forest habitat types based on potential climax vegetation. Reconnaissance plots are inventoried on road or trail transects; plots are located subjectively (but without bias) and are selected to represent the spectrum of environments supporting mature forest communities. Essential quantitative data are obtained using simple, time-efficient procedures, including estimation of canopy-coverage classes for all vegetation. Analysis proceeds through a series of successive approximations utilizing synthesis tables, ordinations, environmental-data correlations, and field-testing of the preliminary classification. Content and format of the final classification are discussed. The classification system was developed during extensive habitat type classification studies in the Rocky Mountains of Montana. Similar approaches are being used in many forested areas of western North America. Forest Sci. 26:52-70.