As the use of fire modeling increases in support of day-to-day nuclear power plant (NPP) applications and fire risk analyses, the importance of verification and validation (V&V) also increases. V&V studies build confidence in a model by evaluating its underlying assumptions, capabilities, and limitations, and quantifying its performance in predicting the fire conditions that have been measured in controlled experiments. This volume documents a V&V study for the Fire Dynamics Simulator (FDS), a computational fluid dynamics (CFD) model, for applications relevant to NPPs. Guidance has been provided by ASTM E 1355, Standard Guide for Evaluating the Predictive Capability of Deterministic Fire Models, including the basic structure of this report. FDS was developed, and is maintained, by the National Institute of Standards and Technology (NIST). Version 4 was officially released in July 2004, and several minor updates had been released as of the time of publication of this report. All of the simulations performed for the current V&V study were done with Version 4.06. With support from the U.S. Nuclear Regulatory Commission (NRC), the FDS Technical Reference Guide for Version 4 was rewritten to follow the basic outline suggested by ASTM E 1355. However, the Guide does not specifically address NPPs. The primary purpose of this report is to document the accuracy of FDS in predicting the results of six sets of large-scale fire experiments that are relevant to NPPs. These results are found in Appendix A and discussed in Chapter 6 of this report. Chapters 2 through 5 provide brief summaries of corresponding chapters within the FDS Technical Reference Guide, which discuss the underlying theory and the numerical methods.