Active brazing plays an important role in many technical processes, in particular in the joining of metallic and ceramic parts. Alloy compositions of interest are mostly either Ag or Cu based with additions of Ti or Zr as active elements. Experimental phase diagram data of most binary systems are avaialable and also some thermodynamic assessments. Ternary phase diagram data, however, are limited. Most commercial thermodynamic databases currently being built (NSLD2, SNOB, etc) focus on solder alloys but do not take into account the active elements involved. The work presented will describe EMPA’s effort in building a self-consistent thermodynamic database for the Cu-Ag-Sn-Ti-Zr system. This includes the assessment of relevant binary and ternary alloying systems with additional experimental data. Coupled with additional thermodynamic and diffusion mobility data possible applications of such a database will be the modelling of interfacial reactions between active brazing alloys and the materials to be joined.