  I discuss the nature of `hotspots' and `jet knots' in the kpc-scale
structures of powerful radio galaxies and their relationship to jet-environment
interactions. I describe evidence for interaction between the jets of FRI
sources and their local environments, and discuss its relationship to particle
acceleration, but the main focus of the paper is the hotspots of FRIIs and on
new observational evidence on the nature of the particle acceleration
associated with them.
