In steel construction, bolted connections offer many constructional advantages over welded connections and are preferred in the field. The use of bolting combined with welding is often required in order to supplement the welded joint. Especially, relatively little attention has been paid to the study of combined use of bolting and welding in high-strength steel applications. In this study, high-strength steel lap joints joined with both welding and bolting were tested and analyzed in order to understand the ultimate joint behavior, examine the extendability of current design recommendations and develop new strength formula if needed. To this end, load-deformation relationship of the combined welded and bolted joint was first derived based on deformation compatibility. The new formula applicable both ordinary and high-strength steels was proposed and verified using test results available. The effect of fabrication sequence between bolting and welding was also evaluated.