Abstract: A method for the liberation of polysaccharide antigens from bacteria or fungi in biological probes or in grown cultures of these probes is described. In the majority of cases such a liberation is necessary in order that subsequently the polysaccharide antigens can be determined immunologically in a manner known per se. This liberation is effected by treating the biological probe or the grown culture with an aqueous phenol solution. A 1-10% phenol solution is conveniently used, with a 2.5% phenol solution being preferred and a 2% phenol solution being especially preferred. The phenol solution is allowed to act on the probe or culture for 5-30%, preferably 15, minutes. No extraction is necessary for the subsequent immunological determination of the polysaccharides.