Mass attenuation coefficients(μ/ρ) and molar extinction coefficients (ε) of gamma rays in some aminoacids,viz.Glycine(C2H5NO2),Alanine(C3H7NO2),Serine(C3H7NO3),Proline (C5H9NO2), Valine (C5H11O2N), Isoleucine (C6H13NO2), Aspartic acid (C4H7NO4), Lysine (C6H14N2O2), Glutamic acid (C5H9NO4), Asparagine (C4H8N2O3H2O), Histidine (C6H9N3O2), Tyrosine (C9H11NO3), Tryptophan(C11H12N2O2) and Cysteine(C6H12N2O4S2),have been calculated at the photon energies 123, 360,511,662,1170,1280and 1330 keV.The effective atomic number and electron density have also been derived and the results are discussed.