A new data hiding method is proposed for embedding a bit-string message into the structure of object groupings in a drawing. The objects in a drawing are grouped skillfully according to the message data to be embedded as well as the inter-object distance relationships between the objects. The groupings of objects in the resulting stego-drawing are visually imperceptible and robust against translation, scaling, rotation, and mirroring attacks. Possibilities of embedding variable-length message data into drawings are demonstrated for different data hiding applications, including data authentication, copyright protection, and covert communication. The method can be applied to a variety of graphic drawings, including flowcharts, network diagrams, circuit schematics, floor plans, etc. Good results obtained from experiments conducted on Microsoft Visio drawings are shown to confirm the feasibility of the proposed method.