AbstractOrientation properties of polymer single‐crystal suspensions in an electric field are studied by Kerr effect and light scattering. It is shown that all the crystals are fully oriented in direction parallel to the electric field for relatively weak field strength (400 V/cm). Kerr‐effect measurements carried out in a.c. electric field indicate the existence of an “electrical” relaxation time (10−2 – 10−3 sec) which is very different from the rotationnal relaxation time (0.1 – 0.5 sec). The orientation property of the polymer crystals is explained by the assumption of the presence of electric charges possessing a certain mobility inside the crystal. The use of Kerr effect measurements is proposed for determination of crystal concentration in suspensions of polymer single crystals.