In this paper, we will describe an apparatus for measuring the through-plane electrical conductivity and also discuss its calibration. This paper describes operating procedures that were used and their effects on conductivity measurements. The following factors were found to affect the measurements accuracy and reproducibility: (i) the method used to polish the copper electrodes, (ii) the nature of the disk used to ensure a good electrical contact between the electrodes and the sample and (iii) whether these disks were reused or not. A 2 mu ohm drift was observed in the resistance measurements on a 24-h period. Two calibration methods were studied. The first calibration method was developed to calibrate the conductivity apparatus using power resistors and we were able to determine that a systematic error of 60 mu ohm was present. A second calibration method was then used to measure the electrical conductivity of two Poco graphite samples. Using our apparatus, the electrical conductivity of AXF-5Q and DFP-2 Poco graphite samples were both (60-210 mu ohm cm) lower than their reported statistical value of 1470 and 1500 mu ohm cut, respectively. (c) 2005 Elsevier B.V. All rights reserved.