Abstract.A horizontal layer containing a miscible mixture of two fluids can produce dissipative solitons when heated from below. The physics of the system is described, and dissipative solitons are computed using numerical continuation for three distinct sets of experimentally realizable parameter values. The stability of the solutions is investigated using direct numerical integration in time and related to the stability properties of the competing periodic state.1. Introduction. Many fluid systems exhibit spatially localized structures in both two [2,4,5,7,9,14,16] and three [10,23] dimensions. Of these the localized structures or convectons arising in binary fluid convection are perhaps the best studied. These states are similar to localized structures studied in other areas of physics [1] despite the fact that fluid systems must always be confined between boundaries. On the other hand in fluid systems the length scale is typically set by the layer depth or the distance between any confining boundaries instead of being an intrinsic length scale selected by a Turing or modulational instability. As a result when we speak of localized states in binary fluid convection we mean states that are localized in the horizontal direction only. In this sense the problem resembles laser systems in short cavities in which the standing wave structure in the longitudinal direction remains of paramount importance [15].In fluids dissipation, whether through viscosity or thermal diffusion, is generally of great importance. For example, it is responsible for the presence of a finite threshold value of the Rayleigh number, a dimensionless measure of thermal forcing, for convection to occur. As a result the solitons of interest in the present article are strongly dissipative and hence require strong forcing for their maintenance. States of this type cannot therefore be understood in terms of (an infinite-dimensional) Hamiltonian system with small forcing and dissipation.In this paper we study localized states in binary fluid convection in a horizontal layer of depth h heated from below. Binary liquids, such as water-ethanol and watersalt mixtures or mixtures of He 3 -He 4 at cryogenic temperatures, are characterized by a cross-diffusion effect called the Soret effect that describes the diffusive separation