Three dimensional reconstructions of 15 pachytene nuclei of Schizophyllum commune have revealed in each nucleus I 1 distinct synaptonemal complexes, demonstrating a haploid chromosome number of 11. Each bivalent contained one short region of condensed chromatin marking the position of the centromere. The synaptonemal complex of each bivalent contained from 0 to six recombination nodules. A high correlation was found between the total length of the synaptonemal complexes in a nucleus and the number of recombination nodules. Total synaptonemal complex length correlated only weakly with the nuclear volume.