Fibre maturity is regarded as a central characteristic of cotton fibre through its direct and indirect correlation with physical and chemical properties of commercial and technical importance.  SiroMat is an automated version of the polarized light microscopy technique, which analyzes interference colours transmitted by cotton fibres when they are placed between crossed polars and a first order retardation plate. The percent areas of colours in images of fibre snippets relate directly to fibre maturity.  Moreover, because fibres are analyzed on an individual basis a maturity distribution for a sample can also be measured.  In this study two sets of cottons with the same average Micronaire but with different fibre maturity values as measured by SiroMat were processed from raw fibre through to dyed finished knit fabric.  The objective of the study was to examine the sensitivity of SiroMat average maturity and distribution values in predicting differences in yarn, and griege and dyed fabric quality.  Results of the study demonstrate the relevance of SiroMat test results in terms of predicting fibre maturity related quality problems and the potential for SiroMat to be used as a tool for managing mill laydowns.