Designers use drawings to explore alternatives and to test ideas. We report here on two studies on design and drawing. The first study of design drawing symbols aims to determine whether and to what extent it is possible to infer, interpret, or even guess what a designer was thinking about by looking at the drawings she has made. In the second study we examined a collection of drawings for the design of a house to investigate the systems of design transformations. Drawings are characterized by drawing style, projection type, and key elements. We analyzed the relationships among the drawings and developed a notation system for documenting these relationships.