This study investigates the behaviour of, and evaluates the benefit accruing to, shear critical reinforced concrete beams, when provided with vertical stirrups spaced at decreasing intervals along the axis of the beam, but with the same amount of web reinforcement per unit beam length. Tests are carried out on three reinforced concrete beams, identical in geometry, flexural reinforcing, amount of web reinforcement per unit span length, material properties and test details. The only varable is vertical stirrup leg spacing along the span. The beams are loaded at half point on a simple span of 2500 mm and all fail in shear. Experimental results demonstrate that, as stirrup spacing decreases, there is a strength gain at ultimate. Besides increased carrying capacity, closer spacing of shear reinforcement results in more beneficial deformational characteristics. Transverse deflections and crack widths decrease as stirrup spacing decreases. The test results establish the desirability of using stirrup reinforcement in practice at as close an interval as possible, along the member length, keeping the amount of web reinforcement per unit length unaltered. This beneficial aspect of using closer stirrup leg spacing than the maximum permitted by codes is not found in the available national building codes for structural concrete. Notation d effective depth of the beam f 1 c cylinder compressive strength (psi) Research significanceAn accurate mathematical model to represent shear in concrete structures is still elusive, despite many decades of experimental research and the use of highly sophisticated analytical tools. Consequently, shear design of concrete beams remains empirical. The search for better design methods is still a preoccupation of many researchers. Research on simpler, more convenient and effective stirrup detailings than the conventional closed stirrups has been meagre to date. Behra and Rajagopalan (1969) pioneered notable research in this area. In three beams, in place of conventional closed stirrups, two-piece stirrups were tried. Lap in one beam was provided in the top face, but adequate development length was not there, with the wrong assumption that maximum stress occurred only at the stirrup mid-height; failure was at 95% of its rated shear. In another beam, lap was provided on the side faces and a lap length of 171 mm for 6-mm stirrups was not adequate; it was reported to fail at 89% of total strength. The final conclusion was that the slight loss of ductility and strength in the two-piece stirrup could be taken care of by more effective lap length.