In recent years, educational policy makers have expressed increased interest in information about private elementary and secondary school expenditures. However, there is currently no national data collection of the finances of this school sector. A study was initiated for three main purposes: to determine the extent to which expenditure data are routinely collected by private school associations, to draw on the data available from private school associations so as to develop preliminary national estimates of such expenditures, and to determine whether the associations' surveys provide an accurate assessment of national estimates of expenditures or whether additional sources of data are required for this purpose. Data from three associations were acquired and analyzed (National Catholic Education Association, Lutheran Church--Missouri Synod, and the National Association of Independent Schools). Estimates of private school expenditure are broken down by total expenditures, estimated expenditures by sector, and estimated capital expenditures. It was estimated that the total operating expenditures for the roughly 26,000 private schools in the United States were between $16.4 and $17.7 billion in 1991-1992. It was concluded that precise estimates of private school expenditures cannot be obtained by relying solely on data provided by private school associations because most associations do not collect data on school finance. Seven appendices detail the private school associations contacted, sample estimate of average per-pupil expenditures, and other information. (RJM)