Abstract. Indonesia has plenty of fly ash as waste materials of coalburning thermal power stations. Fly ash was usually used as a supplementary cementitious material in concrete. One of the basic materials of concrete is fine aggregates which are taken from natural resources. Substitution of fine aggregates by using high volume fly ash concrete (HVFAC) can save the natural deposit of fine aggregates. Fly ash with the portion of 50 %; 60 %; and 70 % as replacement of fine aggregates in concrete was carried out to study the effect on the shear strength of reinforced concrete beam through an experimental program. Eight beams were cast and tested. Two beams were cast and made of normal concrete as control beams, while six others beams were cast and made of HVFAC as replacement of fine aggregates by mass (two beams with 50 % of fly ash; two beams with 60 % of fly ash; two beams with 70 % of fly ash). There were no shear reinforcements in the shear-test regions of the beams. The experimental results show that the load-carrying capacities of HVFAC beams increased with the increase of the portion of fly ash as replacement of fine aggregates.