Kosterlitz-Thouless properties of c-axis-oriented high-T, superconducting YBa2Cu307 „ thin films were examined. The current-voltage characteristics over a wide current range obeyed a power-law relationship. The exponent u(Tj showed a "universal jump" at T, . The exponential inverse-square-root reduced-temperature dependence of the resistance above T, was consistent with a two-dimensional (2D) behavior of the thin films. Excess conductivity due to thermal fluctuations of the order parameter above the mean-field transition temperature T,o was also measured. However, the paraconductivity showed a 1D-like behavior at temperatures close to T,o and further complications at higher temperatures. This 1D-like behavior could be the result of imperfections of the dimensionality of 2 in the polycrystalline sample.