A study has been made of the radiolytic behavior of dilute, neutral, oxygen-free aqueous solutions of CH 3 CN and <tex-math>${\rm C}_{2}{\rm H}_{5}{\rm CN}$</tex-math>. Small-molecular products were identified as RCHO, NH 3 , CO 2 and H 2 . The decomposition of nitrile is followed by high yields of formation of the nonvolatile nitrogen-containing compounds, G(N). The irradiated solutions exhibit a positive biuret reaction. Several amino acids were identified among radiolytic products, and glycine and alanine were found to be the most abundant for CH 3 CN and <tex-math>${\rm C}_{2}{\rm H}_{5}{\rm CN}$</tex-math>, respectively. Their yields increased after strong acid hydrolysis of the irradiated samples. The free radicals formed by reactions of RCN with H, OH, and <tex-math>$e_{{\rm aq}}{}^{-}$</tex-math> were found to be important for the phenomena observed. It has been suggested that the positive biuret reaction, ir spectra, and the release of amino acids on acid hydrolysis provide some evidence on the formation of peptidic materials and might be of interest for the evaluation of the role that ionizing radiation might have played in prebiotic chemical evolution in aqueous media.