This article briefly reviews the seismic design load and zoning scheme proposed by the NZNSEE Bridge Study Group and discusses subsequent work in improving the underlying estimates of New Zealand seismic hazard. The loading scheme, published in 1980, was based on contemporary knowledge of seismic hazard in New Zealand and was innovative in its format which was chosen to give the designer flexibility in selecting the degree of ductility built into the structure, and the return period of the design motions. Difficulty in estimating the design spectra for the NZNSEE study prompted a number of research projects at Canterbury University directed towards a thorough analysis of seismic hazard in New Zealand, expressed directly in terms of acceleration response spectra. These studies, together with complementary work by the SANZ Relative Earthquake Risk Subcommittee are described and discussed.