Morphology is one of the basic characteristics of porous layers. For electrochemically grown pores, morphology is strongly dependent on the starting phase of pore growth, the so-called nucleation phase. This paper addresses uniform and nonuniform nucleation of pores on the surface and consequently the development of pores into the bulk of the following semiconductor substrates: Si, Ge, and III-V compounds (GaAs, InP, and GaP). It was found that nonuniform nucleation can cause formation of domainlike porous structures in all investigated semiconductors. However, depending on the anisotropy of the substrate, these domains show significant differences between them. The particularities of each type of domains are discussed. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.1940847] All rights reserved.