Cytochemical quantitative reactions either for DNA or proteins were performed on spermatozoa in the last stages of the sperm cytodifferentiative process. The analysis of the discrepancy between the expected (1C amount) and the evaluated reaction intensities sheds light on the chromatin condensation phenomenon. The high inactivation and protection of the paternal genome in a particularly packed chromatin has generally been regarded as the cause of non-stoichiometric responses by DNA specific reactions. We suggest that this interpretation fits well for specific DNA reactions based on intercalation between base pairs or DNA phosphate groups binding, but for the Feulgen reaction the cause is more complex and pertains to the particular susceptibility of the sperm chromatin to depolymerization by hydrolysis in the Feulgen reaction.