The primary objective of this paper is to promote an understanding of the relationships between geology, convergence and powered support rating. Investigations were conducted at various collieries in the Illawarra Region of N.S.W. (Australia) and the Scottish area of the British Coalfields. Conditions in the two areas are in total contrast: the Scottish area utilises lower load bearing capacity supports due to the "light" (from a rock mechanics point of view) geological structure surrounding the coal measures and the fact that this structure can accommodate relatively large amounts of convergence with few adverse effects. On the other hand the "heavy" geological conditions of the Illawarra region demand a firmer control over convergence and the use of high capacity supports. Results from the investigations conducted are analysed to show how powered support rating and local geological conditions directly affect the amount of convergence which occurs in the central area of a longwall faceline. Depth of cover and height of extraction are encompassed in the overall investigation and an empirical formula is developed to indicate the amount of influence each parameter has on convergence. �� 1988 Elsevier Science Publishers B.V.