The authors show that Hall effect measurements versus magnetic field RH(B) at 77 K permits one to identify extended defects in HgCdTe and to evaluate their basic parameters. Three different groups of samples can be singled out. First, those with the classical RH(B), consisting of two plateaux in weak and strong magnetic fields with a transition which conforms to the theoretical value of the Hall factor in n-HgCdTe, corresponding to the most perfect crystals. The distinctive feature of the second group is a monotonic decrease of RH, which reaches saturation only in very high fields. It is attributed to the presence of a second set of electrons appearing when the constituent dislocation density on the subgrain boundaries exceeds, at a certain misorientation across the boundary, some critical level corresponding to the appearance of a percolation level. For the third group, with RH(B) between those plateaux, a minimum appears. This is connected with the influence of isolated inhomogeneities with conductivity higher than the conductivity of the surrounding medium. This is presumably due to tellurium-rich precipitates, transformed during anneal in the HgTe inclusions.