The sex chromosomal constitution has been determined in various types of human 
leukocytes at interphase by use of fluorescence in situ hybridization with X- 
and/or Y-specific DNA probes. It is found that during aging and differentiation 
of myelocytes into polymorphs there is no significant change in the relative 
frequency of various types of male and female cells with a specific type of sex 
chromosomal constitution. Non-random variability of the relative proximity 
between the X chromosomes within the nuclei is also observed in female cells. 
Moreover, we are the first to determine that sex-specific "drumsticks" and 
"sessile nodules" in female polymorphs originate from the X chromosomes and that 
non-sex-specific "drumstick-like" bodies in male polymorphs are of Y chromosomal 
origin.