Abstract: The present invention provides a peptide which: (i) consists of 10 to 16 amino acids; (ii) has at least 8 cationic amino acids with either (a) a side chain comprising a guanidinium group, or (b) a side chain comprising an amino group, of which no more than 7 are consecutive; and (iii) has 2 or 3 tryptophan residues which are not both, or not all, consecutive, said peptide optionally in the form of a salt, ester or amide, or a peptidomimetic of said peptide. The invention further relates to pharmaceutical compositions containing these compounds, the use of these compounds in therapy, particularly as anti-tumor (e.g. anti-lymphoma) agents and non-therapeutic uses of these compounds.