[en] A study of electrically inactive defects has been performed on CdTe single crystals by two different experimental techniques: the low temperature thermal conductivity measurement -it has been used as a tool to study crystal defects, such as clusters, stacking faults or point defects-; the X-ray topographie -it completes the first method in showing large aggregates (resolution of 1μm) dislocation arrays or structural defects-. The following observations regarding the experiments are worth noting. CdTe crystals (undoped, Cl or In doped) have been grown by melting zone or THM. Microprecipitates are found in all CdTe crystals. The concentration varies from 10¹⁴ up to 10¹⁵cm^-3 and the mean diameter reaches 100A or more. This concentration is independent on the doping level and on the crystal growth process. The presence of such a precipitation is probably associated with the chemical and thermal growth conditions of the crystals. The K(T) curves fit by the Callaway phenomenological model indicates a point defect concentration of about 10¹⁸cm^-3. The isotopic mass deviation introduces only a concentration of 7x10¹⁷cm^-3. The excess is ascribed to several origins such as nonstoichiometry in CdTe, doping, chemical impurities or Vsub(cd). In X-ray topography large precipitates appear only in crystals not intentionally doped and melting zone purified or in CdTe:Cl. No correlation is found between large and micro precipitates. Dislocations with atmosphere appear also with a low concentration of about 10⁴cm^-2