Nanoelectromechanical systems could have applications in fields as diverse as ultrasensitive mass detection(1-3) and mechanical computation(4-6), and can also be used to explore fundamental phenomena such as quantized heat conductance(7) and quantum-limited displacement(8,9). Most nanomechanical studies to date have been performed in the frequency domain. However, applications in computation(10) and information storage(11) will require transient excitation and high-speed time-domain operation of nanomechanical systems. Here we show a time-resolved optical approach to the transduction of ultrahigh-frequency nanoelectromechanical systems, and demonstrate that coherent control of nanomechanical oscillation is possible through appropriate pulse programming. A series of cantilevers with resonant frequencies ranging from less than 10 MHz to over 1 GHz are characterized using the same pulse parameters.