A frequency-agile antenna design is proposed that uses a fluidic-enabled reconfigurable reactive loading mechanism. The tuning mechanism offers the ability to change the capacitance of an electrically short, hollow coaxial line that is filled with a low-loss dielectric fluid. The frequency response of the antenna can be tuned by altering the material properties of the fluid contained within the coaxial line-and subsequently changing the loading capacitance. This letter presents design details and measured results. \ 2002-2011 IEEE.