Boar spermatozoa were examined for the simultaneous assessment of DNA fragmentation and the nuclear protein matrix using a specific variant of the Sperm Chromatin Dispersion (SCD) test that allowed direct visualization of DNA and nuclear proteins under standard conditions of chemical lysis. Nuclear proteins remaining after lysis were stained with the fluorochrome 2,7-dibrom-4-hydroxy-mercuryfluorescein for specific protein staining. DNA and nuclear protein staining procedures were conducted on untreated-control (no lysis) and treated sperm cells (lysis) resulting the identification of 3 cell types (1) lysis untreated cells; (2) lysis treated cells showing non-fragmented DNA and (3) lysis treated cells showing fragmented DNA. DNA damage was also purposely induced following incubation of sperm in 0.015% H2O2 for 48h at 37C and correspondingly stained for DNA fragmentation and protein. Non-lysed control sperm (1) nuclei showed no halo and stained strongly for protein in the post-acrosomal region. Lysed spermatozoa with non-fragmented DNA (2) showed evidence of restricted DNA loop dispersions at the caudal extremity of the sperm head and a more homogenous but similar distribution of protein matrix in comparison to lysis untreated spermatozoa. Lysed spermatozoa with fragmented DNA (3) exhibited large halos of DNA loops and a loss of the nuclear protein matrix component. Sperm cells exposed to 48h incubation at 37°C and then treated with the lysing agent showed a concurrent and progressive lose of nuclear protein in association with a corresponding increased level of DNA fragmentation. A discriminant analysis of quantitative fluorescence using digital image analysis and conducted after SCD processing, revealed that evaluation of DNA fragmentation and protein could be conducted in an automated system. 97% of the total analyzed cells were accurately classified according to previously defined cell types (1, 2 and 3). The results of the current study demonstrate a synergistic relationship between that of nuclear protein alteration and DNA damage in the boar sperm cell. The importance of abnormal nuclear protein alteration to DNA fragmentation and any related effect on fertility remains to be investigated.