A preliminary pulse radiolytic study is reported on transient optical absorption spectra in solid amino acids. Spectra have been obtained by improved Cherenkov Light Self-absorption Method applied during 5.5 s pulses of 10 or 13 MeV linac electrons. Amino acids exhibit a very different type of behaviour: from lack of absorption signal (at the present sensitivity of the system) to strong absorptions in the visible part of the spectrum and the near UV. The absorption may be due to the electron trapped in lattice imperfections or to the formed free radical. Comparison of spectra in a variety of preparations (hydrochlorides, salts of amino acids and sets of related compounds) suggests a free radical origin of spectra. All transient absorption disappear within a fraction of a second. Free radicals turn by deamination and/or decarboxylation into more stable species detected by ESR.