The stability of dolos armour blocks against wave attack has been investigated in wave model studies. Simple definitions to describe the block movements are introduced and the following results are discussed: 1. The stability of dolos slopes against regular waves and the influence of the slope. 2. The stability of dolos slopes against irregular waves that are not Rayleigh distributed. 3. Comparison between the stability of dolos, natural stones and cubes. 4. The influence of the surface roughness of the dolos model blocks. 5. The applicability of Hudson's formula.