By using directed and directional drilling methods, the length of boreholes can be increased without losing accuracy. For the efficiency of these drilling technologies, process related aspects and geological conditions must be considered carefully. The stability of borehole walls is essential for most directional drilling methods. This thesis contains an extensive literature research, to gain a better understanding of different drilling techniques. This research includes not only a detailed description of the various drilling methods and their basic principles but also the description of flushing technologies. Furthermore, various influence factors on the drilling speed, the geological as well as the process- related aspects that may cause boreholes to deviate from their intended course, are shown. After that, the terms directed as well as directional drilling are defined and the procedures currently available are described. In the third part of the thesis, drilling data from a construction project are analysed. Therefore, drilling and surveying data from 18 boreholes, located in six different areas are evaluated. The survey data includes recordings from camera surveys, which were carried out in each of this six areas. Data analysis starts with a separation of sections with successful control manoeuvers. Drilling and surveying data are used combined during this process. Three zones are defined, based on the quality of the borehole wall using the camera survey data. Subsequently, the previously filtered drilling data is assigned to these defined zones. Finally, an evaluation is performed that contains those areas, in which the drillings could be controlled with the most significant success. This evaluation showed that there are two different ways possible to control drillings. The first option is the intentional up-hole control, which seems to be possible in areas of low drilling progress and high mud pressure. Whereas, the second option is to form wedges under the casing as a result of material collapsing into the borehole. However, this behaviour cannot be influenced directly by the operator. It has also been recognised that high drilling rates in combination with low mud pressure indicating very soft formations. In this formations is the widening of the borehole due to multiple outbreaks possible.