In discussing the galvanomagnetic effects of semiconductors with high electron mobility one has to distinguish four main groups of parameters which influence these effects: (1) For InSb with practically no magnetoresistive effect on a long rod, an increase in resistance by a factor 38 can be reached in 10 000 gauss with appropriate shape (field disk). (2) Layers periodically changing their electron concentration produce an anisotropy of magnetoresistance. For certain specimen orientations the Hall coefficient depends on the magnetic field and a planar Hall effect is observed. Near a step of concentration one measures apparent negative resistances which are caused not by a retrograde current, but merely by rotation of the current lines. (3) If there are more than one type of charge carriers, it is difficult to know the concentration and mobility characteristic of a special type. Because of the high mobility ratio in InSb it is possible to state a hole mobility of 620 cm2/v sec in 150 000 gauss for pure material at room temperature. (4) After elimination of the influences of the above‐mentioned points 1 to 3 one cannot find in InSb any magnetoresistive effect of electrons in the conduction band up to 150 000 gauss. The Hall coefficient is magnetic field independent up to this value of the magnetic induction forn‐type InSb.