The invention relates to a peptide consisting of 2-4 amino acids comprising at least three lipophilic groups of at least 5 non-hydrogen atoms wherein one of the molecule's lipophilic groups incorporates 6 or more non-hydrogen atoms and a second lipophilic group incorporates 10 or more non-hydrogen atoms and wherein at least one lipophilic group incorporates a closed ring of at least 6 non-hydrogen atoms, said peptide having at least one more cationic than anionic moiety, and wherein at least one of the amino acids has a cationic side chain (R group) and at least one of the lipophilic groups is an amino acid side chain (R group), for use as an antitumoural agent and to a peptide consisting of 2-4 amino acids comprising a lipophilic group comprising at least 13 non-hydrogen atoms and one or more closed rings of 4 or more non-hydrogen atoms, wherein at least one of the amino acids has a cationic side chain (R group) and at least one of the amino acid side chains (R groups) is a lipophilic group of at least 4 non-hydrogen atoms, said peptide having at least two more cationic than anionic moieties, also for use as an antitumoural agent.
