For pt. I see ibid., vol. 5, 997, (1972). Widths of JK 0,0 to 1,0 rotational line of a symmetric top molecule CH381Br broadened by N2, H2, CO2, O2, C6H6, CS2 and CCl4 have been measured on a double modulation microwave spectrograph. The experimental data have been compared with the theoretical values as calculated by Anderson-Tsao-Curnutte theory (1962) and Murphy and Boggs theory (1967-68) taking dipole-quadrupole and dispersion forces for the quadrupolar perturbers and dispersion forces for the spherical top perturber CCl4. Molecular quadrupole moments of the quadrupolar perturbers have been determined by Anderson-Tsao-Carnutte theory and compared with other values obtained from different methods. Attempts have also been made to evaluate the molecular quadrupole moment of the absorber CH381Br by including the quadrupole-quadrupole interaction.