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Sperm quality assessment involves qualitative and quantitative indicators, measurable at laboratory level, reflecting to a certain extent the production capacity of sperm and partly the potential fertilization capacity of the ejaculation. In addition, the identification of genes involved in the spermatogenesis mechanism and in the qualitative characteristics of the sperm is invaluable information for the selection of males based on sperm quality. This particular study refers to the comparison of the results of the laboratory classification of 6 boars' ejaculates in high and low fertility based on the quality of the semen from the data kept in the farm from estrus return rates and fertility rates. Furthermore, possible polymorphisms were investigated in five genes P450scc, P45017a, P450arom, 3b-HSD, StAR, after blood sampling. In our research, six boars were involved as semen donors and 48 (6x8) ejaculates were collected over 4 months. The sperm samples were diluted in a final concentration of 30 x 106 sperm / ml and they were used in the farm. At the same time, an aliquot of each sperm sample was transferred within 1 hour to the lab of the Farm Animal Clinic of the Veterinary Medicine School of Aristotle University in an isothermal box and stored at 16-18oC. The parameters that were estimated for each sample of semen were: viability, motility and the individual kinetic parameters of spermatozoa, morphology, biochemical activity of the cell membrane and DNA fragmentation. Vitality and morphology were estimated after the application of double staining eosin-nigrosin. Motility and kinetic characteristics of spermatozoa were examined by computer assisted semen analyzer (CASA). The biochemical activity of the spermatozoa cell membrane was examined by applying the HOST (Hyposmotic Swelling Test) test. The Acridine Orange Test (AOT) was used for the evaluation of sperm nuclear chromatin integrity. In order to isolate the DNA from the blood of each boar, the PCR polymerase chain reaction was performed and the existence of polymorphisms in the 5 genes was investigated. Collected data were analyzed with the use of a General Linear Mixed Model by the statistical software: Statistical Analysis Systems version 9.0 (SAS Institute Inc., 1996, Cary, N.C., U.S.A.) and the level of significance was set at p<0.05. Although our results showed that the total motility varied in normal values in both boar groups, the group of high fertility indicated higher values. Statistical significant differences were found between groups A and B in progressive motility % (“high fertility”: 73,09 ± 2,64, “low fertility”: 64,06 ± 2,64). Additionally, there was a statistically significant difference in the percentage of rapid moving spermatozoa (“high fertility”: 62.88 ± 2.79, “low fertility”: 53.60 ± 2.79) and in the percentage of those who moved slowly (“high fertility”: 9.28 ± 1.94, “low fertility”: 17.00 ± 1.94). Most of the individual kinetic parameters of spermatozoa showed better values in the group of high fertility boars, while a statistically significant difference was observed in VCL, VSL, BCF, WOB between the two groups. No statistically significant differences were found between the two groups of boars in vitality and morphology, but there was statistically significant difference in morphological tail abnormalities ("high fertility ": 3.42 ± 0.23, "low fertility ": 4,47 ± 0,23). As far as the biochemical activity of the spermatozoa cell membrane is concerned, a statistically significant difference ("high fertility ": 60.30 ± 1.16, "low fertility ": 49.24 ± 1.16) was observed. DNA fragmentation was almost zero in both groups. Finally, polymorphisms and mutations in the selected genes were not detected and this fact might require further research.