The DETHERM(R) database contains thermophysical properties of pure substances and mixtures and is one of the worlds largest data collection in this field. DETHERM(R) actually contains 2.85 million data sets for around 100,000 systems (16,000 pure components and 84,000 mixtures). Stored properties are: phase equilibria (vapour-liquid, liquid-liquid, gas-liquid, solid-liquid), azeotropic data, vapour pressures, critical data, caloric properties such as heat capacities, enthalpies and entropies, densities, compressibilities, transport properties such as viscosity, thermal conductivities and diffusion coefficients, surface tensions and electrolyte data such as solubility, electrical conductivities, activity coefficients, phase equilibrium data and transport properties. A bibliographic reference, descriptors and an abstract are always accessible with the numerical data. The article gives an overview about the contents of the DETHERM(R) database, access options and the features of the retrieval software package including numerical subroutines like parameter regression and interfaces to process simulator packages.