Electron spin-lattice relaxation times (T-1e) for the major radicals in gamma-irradiated polycrystalline samples of glycylglycine, L-alanine, 2,4,6-tri-tert-butyl-phenol, and 4-methyl-2,6-di-tert-butyl-phenoI were measured as a function of temperature using pulsed EPR. CW-saturation recovery (CW-SR) were obtained at X-band (9.1 GHz) and S-band (3.0 GHz) between about 10 and 295 K. Inversion recovery, echo-detected saturation recovery (ED-SR), and pulsed electron-electron double resonance (ELDOR) curves were obtained at X-band between 77 and about 295 K. For 2,4,6-tri-tert-butyl-phenoxy radical, which has a single-line EPR spectrum, the recovery times obtained by the three methods were in good agreement and were assigned as T-1e For the three radicals with resolved hyperfine splitting, spectral diffusion caused the recovery times observed by inversion recovery or ED-SR to be significantly shorter than T-1e obtained by CW-SR or ELDOR. Spectral diffusion processes were observed directly by pulsed ELDOR experiments, and time constants for cross relaxation and nuclear relaxation were obtained by modeling the ELDOR curves. For irradiated L-alanine and for the 4-methyl-2,6-tert-butyl-phenoxy radical at some temperatures, the effects of rapid cross relaxation on CW-SR curves could not be fully mitigated even by long saturating pulses, and T-1e could only be determined by ELDOR. For the radicals in gamma-irradiated L-alanine, 2,4,6-tri-tert-butyl-phenol, and 4-methyl-2,6-di-tert-butyl-phenol, methyl group rotation makes significant contributions to Tie at temperatures where the rate of rotation of a methyl group is comparable to the microwave frequency. Activation energies for methyl rotation were determined by modeling the temperature dependence of T-1e at X-band and S-band. In temperature ranges where methyl rotation did not dominate, T-1e was dominated by Raman, direct, or local mode processes.