The clinical relevance of osteoporosis as a frequent systemic skeletal disease is to be found in fractures and their consequences. For prevention of these disease manifestations great importance must be attached to a safest possible diagnosis even before the occurrence of the first fracture and osteodensitometry is a well established technique for this purpose. Among the different measurement procedures DXA (dual-energy X-ray absorptiometry) has become the gold standard worldwide. This method is seen as very reliable and adequately precise. Prerequisites for these characteristics are the correct interpretation of the measurement data obtained by taking into consideration all potential influencing factors which can either false positively or false negatively influence a single value as well as the calculated mean value and the T and Z scores. Thus, exact knowledge of potential sources of error is of crucial importance. The present study shows important sources of error and difficulties in interpretation as well as a discussion of the options for their prevention. For the clinical practice osteodensitometry is to be seen as an important diagnostic component, which can only been interpreted meaningfully with respect to the clinical data.