Synaptonemal complexes (SC’s) were compared to their chromosomes by transmission electron microscopy (TEM) of whole-mount spreads from 42 male chickens. Individual macrochromosomal SC’s were first identified in heterokaryotypes and later by their centromere index. For all nine macrochromosomes (eight autosomes and the Z sex chromosome), the relative length (rl) of each SC corresponded to that of its mitotic and meiotic chromosome, and the centromere position along each SC corresponded to that of its mitotic chromosome. An idiogram was constructed which included the 30 microchromosomes. The idiogram revealed a graded series of SC lengths with a 30-fold difference between the longest and the shortest SC. Microchromosomal SC’s comprised 35% of the genome l