Electro- or electrolessly deposited Ni-P amorphous coatings exhibit some degree of inhomogeneity. This might affect the nucleation process during crystallization of the alloy and therefore its thermal stability. Small angle X-ray scattering (SAXS) gives valuable information about the inhomogeneities in the amorphous state and in some cases about the particle size distribution in as-plated state and after heat-treatment. Two parameters, the radius of gyration, or the average radius, and the so-called invariant, can be used as a measure for the inhomogeneity size and magnitude. The radius of gyration of the particles in the as-plated samples shows a dependence on the P content of the alloy. However, no correlation between the size and the quantity of the inhomogeneities was found. It appeared that the greater the plating solution metal turnover, the greater the SAXS invariant. In general, the inhomogeneities have little or no effect on the primary crystallization of the hypoeutectic Ni-P alloys. (C) 2003 The Electrochemical Society.