The Membrane Deflection Experiment was used to test the mechanical response of freestanding thin film gold specimens. We present stress-strain curves obtained on films 0.3, 0.5, and 0.1 mum thick. Elastic modulus was consistently measured in the range of 53-55 GPa. Several size effects on the mechanical properties were observed including yield stress variations with membrane width and film thickness. It was observed that a width of 2.5 mum and a thickness of 0.5 mum correspond to major transitions in the material deformation behavior. (C) 2003 Kluwer Academic Publishers.