The onset of Rayleigh-Marangoni convection in a vertical annulus heated from below is investigated using linear stability analysis. The results of the present study also show the pattern transitions as a function of scaled gap width and aspect ratio. It is concluded that Marangoni convection can change the fluid pattern in an otherwise pure Rayleigh problem. It is also concluded that the gap width cannot significantly change the Marangoni effect as it is essentially the depth of liquid and Biot number that play a dominant role. (c) 2007 Elsevier Inc. All rights reserved.