Radiation-induced S-butyrylthiocholine Iodide (SBTCI) (C9H20INOS) single crystals have been analysed as results from the use of electron paramagnetic resonance (EPR) spectroscopy. SBTCI single crystals were irradiated with Co-60-gamma rays at 296 K and their EPR spectrum was studied as a function of temperature. The single crystals have been investigated between 120 and 445 K. The single crystal spectra were taken at 5 degrees intervals for the magnetic field H being applied in each of the three crystallographic planes, ab, be and ca. The spectra were found to be temperature independent and radiation damage center is attributed to the CH3CH2CH2CO radical. The g values and the hyperfine coupling constants of the unpaired electron with the protons were determined. The isotropic average value of g-factor and the hyperfine splitting constants are obtained as g(CH3) = 2.037599, g(C2H4) = 2.011297 and a(C2H4) = 20.46G, a(CH3) = 5.6 G, respectively.