This paper presents results of the performance of microfluidic amplifiers of the jet deflection type with hydraulic diameter up to 41 µm, built in silicon using a mixture of wet and dry etching. The amplifier diverts a supply flow into one of two outputs using two smaller control flows. Reversing the control flow, the output flows are switched symmetrically. The output ports were always open to atmosphere, with positive manometric pressure being applied to cause the supply and control flows. Both flow rate and pressure measurements were taken to fully characterize the operation. The devices showed symmetrical flow splitting behavior without any control flows. Increasing one of the control flow, while keeping the other control input open to atmosphere, caused the flow out of the opposing output to increase proportionally with increasing flow gains. The flow gain remained in linear range with control flows up to 40×l0-9 Kg/s. Above that, saturation and output loading effects degraded the flow gain. For supply flows larger than 500×l0-9 kg/s, the average flow gain started to decrease. This is believed to be caused by the onset of turbulence and possibly by the occurrence of normal and oblique shocks in the interaction region. A better understanding of these limiting processes is needed to obtain optimized amplifier designs with larger flow gains.