The robust growth of Information Technology Industry attracts the attention of investors, employees, government and stock market of our country. Its contribution to the economic development is also remarkable. At the same time the boom or recession of this industry brings phenomenal changes in the Indian economy. What makes or mars the growth and value of information technology firms measured in terms of market capitalisation is a problem which requires a deep and analytical examination. This study is undertaken essentially to address this problem. The value of a company is measured by its market capitalisation. The movement of market capitalisation decides the sectoral index of the I.T. sector like CNXIT Index and BSEIT Index. It also plays a key role in the benchmark index of the country like SENSEX and NIFTY. This study analyses and predicts the future movement of market capitalisation of I.T. Industry and also identifies the relationship between market capitalisation and internal factors of a firm's performance.