The present application relates to an immunostimulatory compound comprising an immunostimulant portion and a peptide portion. The peptide portion is not a disease-associated immunogen. Furthermore, the peptide portion has an amino acid sequence in which 75% or less of the amino acid residues are hydrophobic and/or has an isoelectric point of 5 or greater. The compounds of the invention address the problem of systemic distribution of immunostimulants causing unwanted side effects. The inventors have found that the physicochemical properties of the immunostimulant can be controlled by covalent linkage to a peptide. Further physicochemical properties may be modified in a useful manner by incorporating additional features.