Abstract: Straddling dowel for anchoring in a bore having an undercut, comprising an expanding shell (10) having an axial bore (12, 14), which tapers gradually towards the front, for guiding a spreader (26) and having lamellae (28), which are formed by longitudinal slots in the front section of the expanding shell, have an undercut shoulder (20) at the front end and, on their outside, are tapered towards the front in the direction of the undercut shoulder. A guide tube (30) for a setting bolt (40) for driving forward the spreader (26) is used for connection to the rearward end of the expanding shell (10), the guide tube bearing an outer stop (36) and the setting bolt bearing an outer stop (42).