The National Science Foundation (NSF) publishes information on R&D expenditures by American industry based on data collected by the Bureau of the Census. Other organizations publish data on the same issue collected by surveys or derived from secondary sources. Differences exist between these two data. In an effort to understand the reasons underlying the differences, the paper compares the data published by these organizations with the NSF/Census data, concerning R&D expenditure in U.S. industry. The paper describes in detail each of the various sources of industrial R&D data and includes tables to show relative differences between their data and NSF/Census data. A description of the NSF/Census survey is also included. (GA)