Neutron depth profiling (NDP) is a nondestructive technique for the measurement of isotopic concentrations as a function of depth. Using neutrons to probe the first few micrometers of solid surfaces, NDP has become an important tool in the nondestructive analyses for several technologically important elements. The National Institute of Standards and Technology (NIST) has operated a dedicated NDP facility (I) since 1982 using thermal neutrons. Recently, a second, more versatile instrument (2) with improved detection limits was installed as part of the Cold Neutron Research Facility (CNRF) at NIST.