A data acquisition and processing system for analyzing root structure and growth is presented. Two-dimensional drawings are made of root systems growing against the inclined, transparent wall of a rhizotron. For analysis, a root is treated as a number of straight segments between points determined by the position of root apices at successive times of observation and the insertion points of lateral roots. The coordinates of the points are digitized by means of a graphics tablet and the description of the root system completed with information about root branching pattern and root order. From the recorded data, various root characteristics and growth parameters can be computed with a program available from the authors. Use of the data processing system in studies of root architecture is discussed and its application in the analysis of root growth of a pedunculate oak seedling (Quercus robur L.) reported.