The utilization of reinforced concrete as a structural material is derived from the combination ofrnconcrete that is strong and relatively durable in compression with reinforcing steel that isrnstrong and ductile in tension. Maintaining composite action requires transfer of load betweenrnthe concrete and steel. This load transfer is referred to as bond and is idealized as a continuousrnstress field that develops in the vicinity of the steel-concrete interface. The effectiveness of thisrnbond strength between concrete and reinforcing steel is the most important and influenced by arnwide range of parameters. From such parameters this study focuses on the effect of coarsernaggregate and specimen size. rnThe aggregate and specimen size effect on bond strength of concrete and deformed bar isrninvestigated using tensile test method. The parameter includes; concrete of compressive strengthrnof 25MPa with varying maximum aggregate sizes of 9.5mm, 25mm, and 37.5mm, reinforcedrnconcrete member sizes of 10cm*10cm*30cm, 12cm*12cm*40cm, 14cm*14cm*50cm withrncentrally embedded bars of diameters of 10mm,12mm and 14mm respectively are considered. rnBy varying the aggregate size for each specimen the tensile test experiment was done by usingrnUniversal Testing Machine (UTM). From the experiment result increasing of specimen sizerndecreases the average bond strength, this shows that by controlling of all other variables and onlyrnincreasing of specimen size decreases bond strength of the member due to its brittlenessrnbehavior. rnIn the study by increasing of aggregate size the bond strength for a given elongation is constantrnbut the maximum bond strength and elongation decreases as the aggregate size increases, this isrndue to decreasing of number of aggregate and volume of paste in a given section.