The structural heterozygosity of the chromosome complement has been noted in different populations of Allium sativum by different authors (Battaglia 1963, Sen 1973). The chromosome complement of A. sativum is 2n=16. It consists of six pairs of metacentric chromosomes and two pairs with secondary constrictions. The different populations of this species are claimed to have a distinct structural heterozygosity in relation to chromosomes with four secondary constrictions. The other chromosomes too, cannot be strictly paired (Sen 1973). The four chromosomes with secondary constriction can also be easily identified because all the other chromosomes are metacentric. On the basis of this data, the present work was undertaken to utilize Giemsa banding technique, as a tool to investigate the structural heterozygosity in this species. © 1978, Japan Mendel Society, International Society of Cytology. All rights reserved.