This paper describes the design, analysis, and laboratory tests of a prototype viscoelastically (VE-) damped steel frame building. A design approach is presentec.l for a 10-story building with specified highperformance criteria including elastic member behavior and small drift for the 500 year return period design earthquake. Nonlinear time-history analyses with a fractional derivative model for the VEdampers were conducted and are compared with specified design goals. A unique methodology was developed to test the full-scale, lower 3-story portion of the prototype VE-structure which relies on timehistory analyses to determine the displacement for the laboratory test frame. The testing methodology is presented and experimentally observed VE-frame response is discussed. Experimental results are described including overall frame response, local member response, and damper-member interaction.