This paper discusses the main characteristics of the solution chemistry of antimony in relation to its behaviour and fate in natural waters. It is based on a careful and systematic examination of a comprehensive collection of solution equilibrium and environmentally oriented studies, some published more than 100 years ago. General principles are outlined and main unknowns highlighted. Existing information on antimony reactivity in solution is scarce and often relatively old. Studies performed under conditions relevant to natural water conditions are particularly scant.