SUPERTRAPP is an interactive computer program for predicting thermodynamic and transport properties of pure fluids and fluid mixtures containing up to 20 components. The components are selected from a database of 210 components, mostly hydrocarbons. SUPERTRAPP performs phase equilibria calculations and gives the thermophysical properties of all phases and the feed. These results include: Equilibrium properties: density, compressibility factor, enthalpy, entropy, Cp, Cp/Cv, sound speed, Joule-Thomson coefficient Transport properties: viscosity, thermal conductivity Features: bubble and dew point pressure calculations bubble and dew point temperature calculations flash calculations ({T,P}, {T,S} and {P,H}) saturation properties for pure components tables of thermophysical properties with user selected dependent and independent variables ability to add new fluids using minimal data (user must supply at least Tc, Pc, Vc, MW and boiling point) ability to estimate properties of petroleum fractions characterized by an average normal boiling point and an API gravity choice of units FORTRAN source code for property calculations NOTE: Many of the fluids contained in SUPERTRAPP are also available in the REFPROP database. Please see www.nist.gov/srd/nist23.htm for additional details. The REFPROP database is recommended over SUPERTRAPP when REFPROP contains the fluids of interest.