Abstract: Mitomycin derivatives containing substituted dithioethylamino groups at the 7th position are provided. The mitomycin derivatives according to the present invention are superior to mitomycin C with respect to their improved anti-tumour activity and toxicity. More particularly, they exhibit a wider tolerance of dosage against Sarcoma 180A solid tumour as well as a better survival time and weaker bone marrow supression against P388.Furthermore, certain compounds exhibit a high water-solubility which is advantageous for pharmaceutical purposes. Excellent anti-tumour agents may readily be prepared by using the derivatives of the present invention.