Vibration properties of PVF2 cantilevers were studied in vacuum to exclude air loading. Young’s modulus calculated from the resonant frequency at strain levels below 10−4 was 4–8×1010 dyn/cm2, a significantly higher value than hitherto reported with measurements at higher strain levels. As the vibration amplitude and strain was increased, resonance shifted to lower frequencies and hysteresis effects appeared. These effects are attributed to a decrease in Young’s modulus. The elastic loss factor η and Q value, measured from the resonance curve, yielded η=0.025–0.045 and Q=22–40 for the frequency range 8–200 Hz.