Four new sugar:mitomycin C derivatives were synthesized by coupling of N-1 of mitomycin C with tetra-O-acetylglucopyranosyl isothiocyanate and 3,4,6-tri-O-acetyl-2-(N-acetylamino)-2-deoxyglucopyranosyl isothiocyanate. Conversion of each derivative to its water-soluble analogue was achieved by deacetylation, using saturated NH3:CH3OH. Antitumor activity, assessed using the in vivo murine P388 ascitic leukemia system, demonstrated efficacy comparable with the parent mitomycin C. However, unlike the highly myelosuppressive parent drug, optimal antitumor activity is achieved at doses which produce only limited leukopenia.