The National Postsecondary Student Aid Study (NPSAS) is a comprehensive nationwide study conducted by the National Center for Education Statistics to determine how students and their families pay for postsecondary education and to describe some demographic and other characteristics of those enrolled. The study is based on a nationally representative sample of students in postsecondary education, including undergraduate, graduate, and first-professional students at public and private institutions, whether less-than-two-year, two-year, or four-year. Data were available on about 82,000 students, and parents of 18,000 students were selected for a telephone interview. This discussion of survey methodology focuses on: (1) study objectives and design; (2) institution sampling and enlistment; (3) student and parent sampling; (4) institutional records data collection; (5) student and parent surveys; (6) file creation and data analysis; (7) weights and variance estimation; (8) the 1993 NPSAS field test; and (9) a summary and recommendations for survey improvement. Six appendixes provide further details about methodology, including a formulation of the generalized rating model. (Contains 17 figures and 56 tables.) (SLD)