A study of the diameter characteristics of commercially produced Australian wool tops using the Sirolan-Laserscan confirms that there is a good linear correlation between the standard deviation of fibre diameter and mean diameter. Compared with earlier studies using the FDA, for a given mean diameter the currently observed standard deviation and coefficient of variation of fibre diameter were slightly smaller due to instrumental differences. For a range of critical diameters x, the coarse fibre component i.e. ‘% > x”, was found to obey a power law function of mean fibre diameter, μ. Further, these individual relationships could be combined into one simple formula of the form: A comparison of the diameter characteristics of the fibre ends with the usual Tibre diameter measurement has shown that the fibre end properties can he accurately predicted from the usual measurement. Tbere is a linear correlation between the mean diameter of the fibre ends and the usual mean diameter with the fibre ends heing on ave...