HgTe1−xSexsolid solutions have been prepared, withxvarying from 0 to 1. The samples arentype nearx=1 andptype nearx=0, but, due to the high electron‐to‐hole mobility ratio, electronic conudction is dominant in the range 100–400°K in all samples. The concentration of free electrons lies between 5·1016and 3·1018cm−3. Measurements of the Hall mobility &mgr;Hand magnetothermoelectric effect &Dgr;Qshow that, for Se‐rich samples, lattice scattering is dominant in the range 77–400°K and that, near room temperature, &mgr;H∝T−2. For Te‐rich samples, lattice scattering is dominant in the range 200–400°K and, near room temperature, &mgr;H∝T−1. Effective masses have been calculated and it is seen that the conduction band is not parabolic. The detailed band structure and the exact value of the mobility seem to depend little upon structural factors. Forx=0.5 andx=0.9, the electron mobility can reach 12 000 cm2v−1sec−1at 293°K and 30 000 cm2v−1sec−1at 77°K.