<p>Mitomycin derivatives having potent anti-tumour activity having the formula: <CHEM> wherein one of R1 and R2 represents carbamoyloxymethyl and the other represents hydrogen or R1 and R2 are bonded together to form methylene; X is hydrogen or halogen; Y is hydrogen or methyl; Z is hydrogen, methyl or acyl; and n is an integer of 2 or 3.</p>
