The National Human Activity Pattern Survey (NHAPS) was initiated to fill a need for updated activity information on a nationwide scale. The NHAPS, which begain in September, 1992, is a two-year probability-based national telephone interview survey of approximately 10,000 persons that is being conducted by the University of Maryland Survey Research Center assisted by the USEPA to ascertain the time, location, and other characteristics of those activities which are most relevant to estimating pollutant exposure. The survey design, location and activity codes, data examples, and appropriate analyses are described for the NHAPS data base. Time-diary data from this survey will provide standardized activity reports which, when available in early 1995, will be used to refine current human exposure models. Activity diary data have been effectively used in the following types of analyses: descriptive, relational, temporal, and exposure modeling. Examples of these analyses will be discussed and illustrated with data from previous activity surveys, including the recently available California survey. The applicability of these previous analyses to the new NHAPS data will be emphasized.