Weak Affinity Chromatography (WAC) enables high-throughput affinity screening of weak ligand-protein interactions (Kds in the uM - mM range) on HPLC-MS instrumentation which generates instant fragment ranking/affinity data from single concentration screening. Due to features such as its robustness, simplicity, high-throughput and ability to assess very weak binding interactions (mM Kds) while working at low analyte concentrations (<0.1 mM), this technology has proven as an effective alternative for primary Fragment Screening for Fragment Based Drug Discovery. The technology was developed at Swedish universities by Prof Sten Ohlson and co-workers. Weak Affinity Chromatography AB is a subsidiary of Transientic Interactions AB that develops innovative products for Life Science with focus on biochemical weak/transient binding interactions - from which we get our name. keywords: fragment screening, biophysical screening, hit discovery, fragment finding, protein-ligand interactions, intermolecular interactions