In two cultivars of carrots (Daucus carota L) drought stress was imposed at di †erent developmental stages in order to examine how the marketable and nutritional quality was inÑuenced. Experiments were conducted on both a sandy loam soil and a coarse sandy soil. Although drought stress during a 3-week period at any growth stage reduced total tap-root production, the yield of marketable tap roots increased on the sandy loam soil when drought stress occurred just prior to harvest. This was the result of a decrease in the proportion of split roots when drought stress was imposed during this period. An increased risk of infection by common scab (Streptomyces scabies) was seen when drought stress occurred during early growth. Cultivar di †erences in susceptibility to split roots and common scab were observed. SigniÐcant di †erences in chemical composition between cultivars were seen. However, drought stress imposed at a spe-ciÐc growth stage did not inÑuence the chemical composition of tap roots in any consistent manner. When drought stress occurred during early growth on the coarse sandy soil the concentration of dry matter was low and that of potassium and nitrate high. However, the opposite was found on the same soil when drought stress occurred just prior to harvest. Averaging the e †ect of drought periods and cultivars, drought stress was observed to increase the concentration of sucrose in tap roots from the sandy loam soil and decrease that of phosphorus in tap roots from the coarse sandy soil. Various e †ects on magnesium, b-carotene and vitamin C were detected. Severe drought stress increased the storage losses due to the development of diseases.