Hop preparations, their dosing and properties affect the quality of wort and the resulting beer. They impart to wort a bitter taste, hop-like aroma and enhanced protein coagulation. Isomerization products of some hop preparation components are soluble in cold wort. The extent of the isomerization depends on pH, length and temperature of wort boiling. This article provides an overview of the hop preparations used in brewing – hop extracts, granules, modified preparations obtained by isomerization or reduction. It discusses also their composition, dosing, timing and other factors affecting the wort boiling process.