While the advanced art of minimising the installed power for a given speed plays a clear role in the design of containerships, the place of seakeeping is less well established. The incidental character of seakeeping problems at sea incombination with the fact that building for good seakeeping may decrease the container capacity and increase thebuilding costs seems a major reason for this, in addition to the sheer complexity of the issues. The present paperaddresses the last point with an effort to give a complete review of the seakeeping issues in containership design. Basedon recent experience from model tests the work explores the physical nature of the involuntary speed loss in waves andreasons for a voluntary speed reduction (green water loads, whipping accelerations due to bow and stern slamming,engine racing) or change in course (exposure of containers to wave crests, rolling). In addition a review is given of theextreme behaviour that the master would like to avoid altogether, like excessive heel due to loss of stability in followingseas and parametric roll. Based on the results tentative design guidance is formulated.