The use of precast concrete hollow-core floors rose to prominence in New Zealand in the 1980s because of an economic boom at that time and the ease of construction. Their widespread use in New Zealand, a region with high seismicity, and observations made after the 1994 Northridge Earthquake prompted a comprehensive research program to better understand the behavior of hollow-core floors in earthquakes. A number of system-level and component-level tests were conducted and results from this research program helped understand vulnerabilities of hollow-core floor systems and led to improvements in design provisions in the New Zealand Concrete Standard. The research program also provided the basis for the development of a seismic assessment procedure for existing hollow-core floors described in a companion paper. A summary of this research program and key design provisions is presented in this paper. Keywords: floor diaphragm; hollow-core floors; precast concrete; seismic testing.