This document discusses techniques for retrofitting existing structures to improve their resistance to seismic activity. It begins with an introduction to seismic effects on structures and why retrofitting is needed. Then it describes the goals and objectives of retrofitting, which include increasing lateral strength, ductility, and integral action while reducing irregularities. The document outlines the typical steps in a retrofitting process and presents various retrofitting strategies. Global strategies discussed include adding shear walls, infill walls, bracing, and base isolation to improve the overall seismic performance of the building. Local retrofitting techniques aim to strengthen individual members.