SINDA/FLUINT (Ref 1, 2, 3, 4, 5 and 6) is a computer program used to analyze thermal/fluid systems that can be represented in finite difference, finite element, or lumped parameter form. In addition to conduction and radiation heat transfer, the program is capable of modeling steady or unsteady single- and two-phase flow networks, their associated hardware, and their heat transfer processes. Because it is generalized, versatile, and user-extensible, SINDA/FLUINT is a standard in the aerospace industry for modeling thermal control systems. It is also used in the automotive, aircraft, electronics, petrochemical, HVACR (heating, ventilation, air-conditioning, and refrigeration), and process industries.C8R's SinapsPlus™ is a complete graphical user interface (pre- and postprocessor) and model debugging environment for SINDA/FLUINT (Ref 7, 8). SinapsPlus also supports the C and C++ languages in addition to the traditional choice of Fortran for concurrently executed user logic.In this paper, recent improvements to SINDA/FLUINT are described along with developments currently in progress. These improvements include powerful spreadsheet-like manipulations for fast parametric analysis, reduced user logic, and improved self-documentation of models. Work in progress includes the integration of an optimization engine for more powerful design capabilities and for automated test data correlation. Also in progress is the addition of advanced two-phase fluid and mixture solutions such as the modeling of fast-transient nonequilibrium duct flow and the handling of dissolved gases.