The evolution of the Portuguese electronic market made it possible for the ordinary Internet user to buy and sell stocks in the Lisbon Stock Exchange online through several specific sites.

In this work an application was developed in which the potential investor, based only on the historical knowledge of the stock quotation (temporal series) can, with some reliability, make predictions about the future variation of certain stocks quotations and so find business opportunities online.

In this work a database was created for the loading of daily stock quotations, information gathering, verification and values fitness and their insertion in the database. The user interface allows the graphic visualization of stocks quotation series behaviour and the option of selecting pairs of stocks to analyse, weather they are or not in the same area of activity, the measurement of the correlation factor and the period of time for simulation effect. The adaptation of the method used for the analyses of the temporal series is here evaluated through the presentation of some examples of investment simulation. So, for an investor with low knowledge about the functioning ofthe stock exchange market the use of this tool, along with a daily following of stocks quotation evolution, may allow the investment in this kind ofproduct (stocks) with a minimum risk factor.