Mini-rhizotrons, transparent tubes of 60 mm diameter viewed using a high resolution TV camera and micro-rhizotrons, transparent tubes of 25 mm diameter viewed using a boroscope were used to assess the growth of a range of perennial species in both field and laboratory studies. The mini-rhizotron method produces a permanent record of root development on video tape which can later be quantified using image analysis software. The equipment required for this is however relatively expensive ($25,000). In contrast the micro-rhizotron method does not produce a permanent record but uses a grid on the tube to allow direct root assessments and is relatively inexpensive ($1,400). The advantages and disadvantages of these two methods and the type of data they produce is discussed.