A preparation containing an absorption promoter selected from N-acyl amino acid derivatives or N-acyl peptide derivatives represented by the formula: R-CO-A (R is an aliphatic hydrocarbon group, an aromatic hydrocarbon group or an aryl-substituted lower hydrocarbon group which may optionally be substituted, and A is an amino acid residue or a peptide residue), preferably in the presence of a salt at a concentation exhibiting higher osmotic pressure than isotonic sodium chloride solution, and a medicine is found to promote absorption of the medicine through a gastrointestinal organ such as the colon and rectum, and through the vagina.