The technique for determining the fibre fineness of a sample of wool as used in South Africa is outlined. The methods of cutting the fibre bundle into fragments and the mounting of these on a slide are described. The effect of ether used for mixing the wool fragments and the Euparal mounting medium are described. The method of measurement, the system of recording the results and the number of fibres to be measured in Merino wool are recorded. The weight-length method for determining fibre fineness, suggested for arbitration purposes, is discussed and difficulties peculiar to this method are enumerated.