The technical quality, i.e. chemical composition of sugar beet is strongly influenced by weather conditions. Water deficit can cause an increase of the nitrogenous compounds in the beet summarised as harmful nitrogen, and thus lead to reduced sugar recovery. In order to study the influence of water supply on beet quality, in 2000 a field trial with and without irrigation was carried out in Wörbzig near Halle in Saxonia-Anhalt. Beets were harvested every second week from May to October. Total soluble nitrogen, a-amino-nitrogen and nitrate markedly decreased during the season, while with betaine content no uniform tendency was ob-served. Between July and August, a period of very low precipitation, a strong increase in a-amino-N, betaine and total soluble N appeared in the non-irrigated treatment; up to the final harvest, harmful nitrogen remained higher compared to the treatment with irrigation. Thus dry conditions may cause a considerable decrease in technical quality and thereby in sugar recovery.