The birth and success of index option markets have fostered empirical research on their efficiency. While most of the literature focuses on North American markets, studies on European markets are still limited. The aim of the present paper is to provide further evidence on a European market, the Italian index option market (MibO), by testing the validity of the most famous no-arbitrage relationship in the option markets: the Put-Call parity (PCP). The growth of the market, new facts (such as the transition to the Euro and new market rules) and the availability of a broader and better quality high frequency data set make our work different from the previous study on the same market by Cavallo and Mammola(2000). Our analysis highlights the role of frictions in the tests of the PCP and points at a substantial and increased efficiency of the Italian index option market.