Recent advances in cereal genomics have made it possible to analyse the architecture of cereal genomes and their expressed components, leading to an increase in our knowledge of those genes that are associated with the key agronomical traits. Presently, use of a dwarfing gene in breeding process is crucial for the development of modern cultivars. In barley, more than 30 types of dwarfs or semi-dwarfs have been hitherto described. However, only a few of them have been successfully used in barley breeding programs. Both breeding and molecular mapping experiments were undertaken to enhance and evaluate the performance of semi-dwarf barley lines. The semi-dwarfing cultivars had improved lodging resistance and a higher harvest index. There have been a lot of investigations that have contributed new information to our basic understanding of the mechanisms underlying growth regulations in barley. This paper reviews semi-dwarfing genes in barley in general and special attention is paid to mapping of the sdw1/denso locus, changes in protein abundance and associations of the semi-dwarfness with gibberellins.