New nitrosoureido derivatives of di- or tri-deoxy-sugars have been synthesized. Very potent antitumour activity against L1210 leukaemia was exhibited by the compounds derived from methyl 3-amino-3, 4-dideoxy-beta- and alpha- and 4-amino-2,4-dideoxy-beta- and alpha-D-arabino-hexopyranosides, 24, 26, 28 and 29, respectively. In further evaluation against B16 melanocarcinoma bearing mice, only compounds 24 and 26 displayed significant activity. Owing to its lower acute toxicity, methyl 3-[3-(2-chloroethyl)-3-nitrosoureido]-3, 4-dideoxy-beta-D-arabino-hexopyranoside 24 appeared as the best candidate for preclinical studies.