Abstract: A scaffolding system comprises tubular uprights (10) having inwardly extending stiffening and guide flanges (23) for guiding any inserted jointing pieces and braces (15) that may be necessary, and connected with connecting beams (12) by means of bayonet joints (21, 22, 33). Such a bayonet joint comprises a hole (21) in the upright (10) and a locking hook (22) which projects from the end of the beam (12) and which, after it has been turned into its engagement position, is fixed in this position by means of a catch (35) displaceably mounted on the beam for movement into locking engagement with the upright. The inwardly extending stiffening flanges in the tubular uprights have radial recesses provided at a predetermined distance from the ends of the uprights to receive outwardly directed projections on a jointing piece insertable in the uprights.