The volumetric and acoustic methods are used for investigating the interactions of L-serine with drugs ampicillin (AMP) and amoxicillin (AMX) as a 66 function of temperature. Densities and speeds of sound of L-serine in (0.0009, 0.0018, 0.0028, and 0.0038) mol.kg(-1) solutions of ampicillin and amoxicillin have been measured at T = (305.15, 310.15, and 315.15) K and atmospheric pressure. The density and speed of sound data have been used to determine apparent molar volume (V-phi) and apparent molar adiabatic compressibility (K-phi,K-s). The positive values of V-phi and negative values of K-phi,K-s indicate attractive interactions between 61 L-serine and drug molecules. The pair interaction and triplet interaction coefficient for volumetric and acoustic data have also been calculated which suggest pairwise interactions between L-serine and drug molecules. The results have been discussed in terms of various interactions prevailing in aqueous solutions of amino acids and drugs.