A trailer having adjustable elevation is provided which includes a chassis 1 connected with a draw bar assembly 2 by a first linkage means, operating means 8 provided to raise or lower the chassis 1 relative to the draw bar assembly 2, second linkage means connecting pivotal wheel-mount assemblies 4 with the draw bar assembly 2 so that lowering and raising the chassis 1 provides a respective raising, and lowering of the wheel-mount assemblies 4 so that they can be retracted above the chassis 1, the first linkage means including a plurality of link arms 3 adapted to form a substantial parallelogram linkage, between the draw bar assembly 2 and the chassis 1, whereby the draw bar assembly 2 is permitted an arcuate range of motion relative to the chassis 1 while remaining substantially parallel therewith to enable the chassis to be engaged with the ground.