One essential aspect of any CAD system, which has not been addressed adequately, is the capability to support the automatic placement of dimensions of a mechanical drawing. Today, even the most sophisticated CAD systems automatically place dimensions of mechanical drawings without strictly adhering to standard dimensioning rules (e.g., there are usually overlaps, repetitions and misplacement of dimensions). Therefore, the automatically generated dimensions are the starting point for a manual improvement of the dimension positions. In this paper we present a software system for the automatic placement of dimensions in mechanical drawings, incorporated into a commercial CAD system, which is efficient and places dimensions that comply with the basic drawing standards, assigns dimensions to all elements of a drawing, and does not produce redundant dimensions.