A historical review of the development of knowledge of defect formation in semiconductor crystals is given. The treatment starts with zero-dimensional defect types, especially native point defects in Si and GaAs. One-dimensional structural disturbances-dislocations and their patterning-are discussed next. Whereas in Si the total elimination of extended dislocations is well established, in semiconductor compounds, like III-Vs with low critical resolved shear stress, this seems to be impossible. In a further section micro- and macro-segregation phenomena-striations and the effects of constitutional supercooling-are reviewed. Finally, two-dimensional features are discussed. First the interplay between facets and inhomogeneous dopant incorporation is described. Then the problem of twinning, especially in InP, is outlined. The paper is focused on the grassroots from the beginning of the 1950s-the birth of semiconductor melt growth. For each defect type the current state of knowledge and methods of control are indicated. Problems remaining to be solved in the future are summarised. (C) 2004 Elsevier B.V. All rights reserved.