By lifting an epitaxial thin film off its growth substrate, we directly and quantitatively demonstrate how elastic strain can alter the magnetic and electrical properties of single-domain epitaxialSrRuO3thin films (1000 Å thick) on vicinal (001)SrTiO3substrates. Free-standing films were then obtained by selective chemical etching of theSrTiO3.X-ray diffraction analysis shows that the free-standing films are strain free, whereas the original as-grown films onSrTiO3substrates are strained due to the lattice mismatch at the growth interface. Relaxation of the lattice strain resulted in a 10 K increase in the Curie temperature to 160 K, and a 20&percent; increase in the saturation magnetic moment to1.45 &mgr;B/Ruatom. Both values for the free-standing films are the same as that of the bulk single crystals. Our results provide direct evidence of the crucial role of the strain effect in determining the properties of the technologically important perovskite epitaxial thin films. ©1998 American Institute of Physics.