This paper describes and discusses a practical approach to formulating rational and economic procedures for the seismic design of industrial plants and of petrochemical plants in particular, on the basis of the current New Zealand Loadings Code for Buildings, NZS 4203:1976. The authors' firm was engaged as consultants for the seismic design (inter alia) of the Ammonia and Urea Plants and offsites for the Kapuni Fertiliser Complex. This paper is a result of that work. and will also be published in ‘Transactions of the Institution of Professional Engineers New Zealand’.