The recent progress in techniques related to the culture and fusion of plant protoplasts has permitted to perform genetic modifications of numerous crops. Both inter- and intraspecific somatic hybridization have led to the production of many hybrids which display higher ploidy level and more valuable agricultural traits than donor plants. Asymmetric hybridization, which permits to combine only part of the parent genomes, has enabled the introduction of some desirable traits from wild species into cultivated varieties, e.g. new sources of cytoplasmic male sterility and resistance to pathogens or low temperatures. The spectacular achievements in this field involve the species from the Solanaceae, Gramineae, Cruciferaea and Citrus families. On the other band, the culture and fusion of protoplasts have caused some problems which are difficult to overcome. They are related to the appearance of albinotic or dwarf plants, formation of sterile hybrids or genetically instable ones, and also production of hybrids displaying undesirable agricultural characteristics.