A cleaning and disinfecting composition comprises a long-chain alkyl polyamine, such as dodecyl dipropylene triamine; a long-chain quaternary ammonium salt, such as N,N-didecyl-N,N-dimethylammonium chloride; and a metal carbonate salt, such as potassium carbonate, all in aqueous solution. A sequestering agent, a long-chain alkyl polyethoxylate, an alkanolamine and an anti-corrosive agent may also be present. The composition has a pH of at least 11 when diluted to an in-use concentration, and may be used to clean and disinfect hard surfaces, such as medical, dental and surgical implements, walls, floors, sinks and hard furnishing surfaces, or soft surfaces such as bedding, upholstery or clothing. The composition is effective as a virucide, a sporicide, a bacteriocide, a fungicide, and against yeasts and moulds, without harming the substrate cleansed.