1, 2 and 3 kGy had significant effect (p < 0.05) on colour values of pistachio oil. Parameters L⁄, a⁄ and b⁄ were increased with increasing gamma irradiation dose from 1 kGy to 3 kGy. Mexis and Kontominas (2009a) reported that colour parameters b⁄ of hazelnuts increased (p < 0.05) after irradiation at dose of >5 kGy, while colour parameter L⁄ and a⁄ remained unchanged by irradiation. Mexis et al. (2009) reported a decrease in L⁄ parameter (p < 0.05) at dose >3 kGy, while colour parameters a⁄ and b⁄ remained unaffected after irradiation of almond kernels at doses up to 7 kGy.