The　so-called　size　effect　is　understood　as　any　dependence　of　nominal　strength　on　the　structural　size.　The　efforts　on　the　size　effect　of　concrete　structures　have　fallen　into　two　major　aspects,　1)　size　effect　of　concrete　materials,　and　2)　size　effect　of　reinforced　concrete　members.　The　present　study　deals　with　the　former,　that　is,　the　size　effect　of　concrete　materials.　Some　widely　used　laws　for　size　effect　of　concrete　materials　are　assessed,　and　the　experimental　and　numerical　efforts　on　the　size　effect　of　concrete　materials　are　then　introduced.　At　last,　some　suggestions　are　provided　for　the　existing　problems　and　future　developments.　Generally,　establishing　a　global　law　of　size　effect　for　full-scale　concrete,　based　on　fracture　mechanics　in　conjunction　with　the　randomness　of　material　strength　and　the　fractal　characteristic　of　cracks,　is　the　subsequent　research　target.　Furthermore,　the　size　effect　tests　and　the　simulations　with　a　larger　range　of　sizes　shall　be　conducted　to　validate　and　extend　the　new　theory　of　size　effect.　©　2017,　Editorial　Office　of　China　Civil　Engineering　Journal.　All　right　reserved.