The authors report a human sperm suspension method to assess quantitatively the stainability of the spermatozoa chromatin. Analysis of 15 ejaculates demonstrated the existence of a constant percentage of stained DNA in different ejaculated spermatozoa. The condensed chromatin stainability was then compared to the in vitro decondensed chromatin stainability with the finding of an increased uptake of fluorochrome in relation with the nuclear chromatin decondensation. The quantitative spermatozoa chromatin stainability and its decondensation aptitude may be of importance in sperm physiology.