Abstract Measurements of the electrical conductivity, magnetoresistance, and Hall effect were performed on a n-type ferromagnetic semiconductor HgCr 2− x In x Se 4( x = 0.100) single crystal from 6.3 to 296 K in magnetic fields up to 1.19×l0 6A/m. The conductivity decreases rapidly near the Curie temperature T c (≈120 K) as the temperature is raised. A large peak in the magnetoresistance is observed near T c . The Hall effect measurements indicate that the temperature dependence of the conductivity and the magnetoresistance are due mostly to a change in electron mobility. The electron mobility is 1.2 × 10 −2 m 2/V · s at 6.3 K, and decreases rapidly near T c with the rise in temperature. Then it increases slowly from 5.5 × 10 −4 m 2/V · s at 160 K to 7.5 × 10 −4 m 2/V · s at 241 K. This temperature dependence of the electron mobility can be explained in terms of the spin-disorder scattering which takes into account the exchange interaction between charge carriers and localized magnetic moments.