Pioneering research in Brassica microspore culture (1,2,3)rapidly led to the realization that microspores provide a powerful alternative to protoplast culture as a single-celled culture method in plants. These two single-celled systems are fundamentally different, both in tissue origin and in genetic variability. The microspore system improves significantly on the protoplast system by virtually eliminating the large somaclonal variation associated with protoplast selection, by utilizing a true haploid cell system, and by resulting in a more synchronized embryo development that facilitates accurate mutation and selection methods. Most critical, however, are the observations that plant regeneration frequencies in excess of 80% can be readily obtained and that the entire sequence from microspore isolation to plantlet development may take place in as little as 4 wk (4).