The atomic layer epitaxy (ALE) technique has in ten years established a position as one of the methods capable of controlled processing of thin films. A major part of the 500 studies published has dealt with II–VI and III–V semiconductors and with insulating or conducting oxides. The practically unlimited chemical possibilities of ALE should offer possibilities for widening the scale of materials processed so far. In addition to giving a status report, in this review we discuss some obvious future research trends as well as problems involved in the processing of new materials. To illustrate the difficulties in processing thin films of complicated chemical composition the case of YBa 2Cu 3O 7− x is presented