Elastically supported cylinders in cross flow are investigated experimentally and by numerical simulation. For very low values of cylinder mass ratio, it is found that the oscillation frequency is controlled by vortex shedding, with no lock-in to the mechanical frequency. In the numerical simulations the systems studied have zero mass and damping. A range of values of spring constant, including zero, is investigated at Reynolds number 100. It is found that the oscillation frequency stays in a narrow range 0.15 < fd/U∞ < 0.2 and the amplitude is in the range 0.4 < A/D < 0.6, eventually decreasing at large values of spring force.