The paper discusses the dynamic behavior of a 16-story building model representing an idealized office building. The model is subjected to “standardized” types of ground motion, and the dynamic shears between adjacent stories are measured. The rigidity of the first story is varied so that the effect of a “flexible” first story on the dynamic shears is demonstrated. It is concluded that flexibility in the first story decreases the dynamic shears everywhere in the building when the same degree of “tuning in” with the ground-motion frequency is postulated. Moreover, it is concluded that current practice design rules are in fair agreement with the shears that may be expected when the building is vibrating in or near its fundamental mode, but that current practice does not allow for shears due to the higher modes unless a comparatively flexible first story is used.