The surface of the zygotes of Schizosaccharomyces pombe was studied by observing fluorescence following primulin treatment. Conjugation occurred only at the poles. Competence to fuse was independent of actual pole growth and pole ontogeny (old or new pole). The cells were competent to fuse throughout the first three-quarters of the cell cycle. Morphological criteria indicate that cell pairs are not synchronized at the moment of fusion. The length of the G1 phases of individual conjugating cells apparently ranges from 0.1 to 0.7 of the cell cycle duration.