The　main　objectives　of　this　study　are,　on　one　hand　to　present　an　experimental　campaign　on　the　shear　failure　behavior　of　reinforced　concrete　(RC)　beam-to-column　joints　having　different　structural　sizes,　especially　full-scale　joints,　and　on　the　other　hand　to　evaluate　the　possibility　of　the　existence　of　size　effect　on　the　corresponding　nominal　shear　strength　of　the　RC　joints.　The　test　results　of　geometrically　similar　interior　RC　beam-to-column　joints　with　the　joint　width　ranging　from　300　mm　to　900　mm　under　both　monotonic　and　cyclic　vertical　loadings　are　reported　in　this　study.　The　effects　of　stirrup　ratio　and　loading　type　on　the　seismic　shear　failure　behavior　at　the　core　region　of　the　joints　are　studied.　Moreover,　the　size　effect　of　the　corresponding　nominal　shear　strength　of　the　RC　beam-to-column　joints　is　also　explored.　The　experiment　results　demonstrate　that　the　failure　modes　of　RC　beam-to-column　joints　with　different　structural　sizes　are　similar.　There　is　a　significant　size　effect,　namely,　the　larger　the　structural　size　of　the　joint　is,　the　smaller　the　nominal　shear　strength　at　the　core　region　of　the　joint　is.　Increasing　the　structural　size　causes　poor　ductility　capacity,　fast　degradation　of　stiffness　and　more　dissipation　energy.　Moreover,　cyclic　loading　makes　the　size　effect　on　shear　strength　of　RC　joints　stronger.　The　stirrups　weaken　the　size　effect　on　shear　failure　since　the　tested　shear　bearing　capacity　is　mostly　carried　by　the　concrete　part.