Historians of cartography occasionally refer to cartographers’ horror vacui, that is, their fear or hesitancy to leave spaces blank on maps that might be filled with decorations. Some scholars have denied that this impulse was a factor in the design of maps, but the question has never been examined carefully. In this talk I will undertake such an examination, showing that horror vacui was indeed an important factor in the design of maps, at least for some cartographers, from the sixteenth to the early eighteenth century. Some of the factors that motivated cartographers’ concern about empty spaces will also be examined, as will maps by cartographers who evidently did not experience this fear. In the eighteenth and nineteenth centuries maps began to be thought of as more purely scientific instruments, cartographic decoration declined generally, and cartographers managed to restrain their concern about spaces lacking decoration in the interest of presenting their work as modern and professional.