The effects of ..gamma.. radiolysis on adamantane-d/sub 16/ and adamantane-d/sub 16/ containing 2-methyltetrahydrofuran solute molecules have been examined via X-band 9.5-GHz and Q-band 35-GHz electron spin resonance at temperatures down to 77/sup 0/K. Adamantane-d/sub 16/ appears to produce at least two radical species, a fact that cannot be deduced from X-band ESR alone. 2-Methyltetrahydrofuran produces two distinct radicals and hyperfine splitting constant values have been assigned to each species. A third radical is formed from 2-methyltetrahydrofuran at high temperature, but is presently unidentified. These two radicals are believed to be formed in ..gamma.. radiolysis of 2-methyltetrahydrofuran glass, but they do not seem to suffice to entirely explain the observed spectrum in the glass. (auth)