Biocidal active substances are called in-situ generated active substances if they are generated from one or more precursors at the place of use, like active chlorine generated from sodium chloride by electrolysis, active bromine generated from sodium bromide and sodium hypochlorite and hydrogen peroxide generated from sodium percarbonate by dissolution in water. The approval of these substances in the European Union (EU) requires evaluation of the generated active substance and of the precursor(s) it is generated from. The regulation of in-situ generated active substances in the EU under the Biocidal Products Regulation (BPR) and its predecessor the Biocidal Products Directive (BPD) has been complex. With the recent adoption in the EU of the document “Management of in situ generated active substances in the context of the BPR” a harmonised framework is now in place. The document clarifies which in-situ generated active substances are included in the Review Programme, describes the possibilities to add ‘new’ combinations to the Review Programme and clarifies the different obligations for industry. ECHA is providing guidance on in-situ generated active substances and notifications for ‘new’ combinations will have to be submitted via the Register for Biocidal Products (R4BP). The presentation will: i) summarise the previous and current regulation of in-situ generated active substances under the BPD and BPR, respectively; ii) describe in detail the current guidance from the Commission; iii) describe the current status of the on-going evaluations and technical and scientific aspects related to these evaluations.