The preparation and properties of the lipopolysaccharide standard of S. abortus equi (Novo-Pyrexal) are described.Preparation involves extraction from PhOH/H2O followed by PhOH/CHCl3/petroleum ether extraction, ultracentrifugation, electrodialysis, and conversion to the Na salt form.The preparation is free of proteins, nucleic acids, and glycans.The structure and composition of the preparation are given.Novo-Pyrexal was biol. active for local Shwartzmann reactivity, progenicity, toxicity, mitogenicity, reactivity towards complement, and tumoricidal activity.