The study consisted of applying 7 (seven) technical analysis tools to 7 (seven) of the most representative shares that make up the COLCAP index. This was done in order to test the hypothesis supporting weak market efficiency in the Colombian stock market. To determine this, the possibility of achiving higher returns with an active investment strategy was compared to buying and holding onto a share. Three different approaches were used in the study. At first the analysis tools were applied to the theory described for determining each indicator that is measured in the index and the initial results showed that the tools are not trustworthy for predicting future price performance. Following this, the stop loss rule was applied giving better results than the previous ones. However, the results broke down when factoring in transaction costs. In a third attempt, an investment strategy which combined some indicators with the stop loss rule was used. This approach was out-performed by the passive investment strategy. Lastly, after the analysis stage, the strategy was validadted in the real world. In some cases higher returns were achieved compared to the buy and hold strategy. Even so, the low level of trustworthiness of the rules for predicting future share value behaviour casts doubt on the performance of the active strategy. The above leads to the conclusion that applying technical analysis tools to the Colombian stock market does not provide sufficient systematic and reliable results to warrant using them in everyday practice for anticipating market behaviour. Thus, the results back up the hypothesis of weak market efficiency in the Colombian stock market.