This study evaluated p-type silicon diodes for use in in vivo dosimetry in clinical electron beams. A calibrated p-type silicon diode detector was used to measure the dose received by the patient in the centre of the field. Readings were corrected for energy, temperature and stand-off of the electron applicator from the patient surface. The mean difference between measured and prescribed dose was 1.04% (95% CI 0.72 to 1.36 %).