The TEXSAN thermal-hydraulic analysis program was developed to simulate buoyancy-driven fluid flow and heat transfer in spent-fuel and high-level nuclear waste (HLW) shipping applications. The TEXSAN design has sufficient flexibility to conduct full cask analysis as well as small-scale heat and mass transfer simulations on a rod-to-rod basis within an individual fuel assembly. As part of the TEXSAN software quality assurance program, the software has been subjected to a series of test cases intended to validate its capabilities. The validation tests include many physical phenomena that arise in spent-fuel and HLW shipping applications. Some of the principal results of the TEXSAN validation tests are described, and they are compared with solutions available in the open literature. The TEXSAN validation effort has shown that the TEXSAN program is stable and consistent under a range of operating conditions and provides accuracy comparable with other heat transfer programs and evaluation techniques. The modeling capabilities and the interactive user interface employed by the TEXSAN program should make it a useful tool in HLW transportation analysis.