A total of 40 male and 40 female mice of equal body weight were used in the present study. Whole body gamma (60Co) irradiation was carried out at 400, 800 and 1200 rad. Life span and several parameters of body composition were measured. Cumulative mortality precentage was lower in irradiated females in comparison to males. Ionizing radiation induced reduction (P < 0.01) in body weight, total body water with its two compartments (extra-and intracellular), fat-free body with its component (body cell mass and extracellular tissue), fat-free dry solids with its constituent (body protein and body ash), body potassium and body fat. While all of the above mentioned body composition parameters decreased (P ≤ 0.01) following whole body irradiation, the rations between the body water to these parameters increased (P ≤ 0.01). Sex difference was noticed either for the parameters or for the ratios.