Aim of this paper was to assess the values of genetic parameters which have crucial influence on selection effect. Values of phenotype variability as well as coefficient of heritability and correlations between milk yield traits analyzed in this research are shown in this paper. The paper includes 1109 first standard lactations of black and white breed cows, offspring of 9 fathers bred at 7 farms of Agricultural Corporation Belgrade during the year 2008. The paternal influence was researched as well as breeding farm, calving season influence to phenotype expression and variations of milk yield traits in standard lactation. Statistically very significant (p lt 0,01) influence of the bull, farm and calving season on phenotype expressiveness, variability of milk yield, milk fat yield and protein yield in standard lactation was determined. Determined values of heritability for milk yield traits, milk fat contents, protein contents in milk, milk fat yield and milk protein yield were: 0.115, 0.049, 0.017, 0.119. and 0.111, retrospectively. Genetic correlations coefficient values of milk yield traits were from: -0.746 (milk fat yield - protein content) to 0.983 (milk fat yield-protein yield).Cilj rada bio je da se procene vrednosti genetskih parametara koji imaju presudan uticaj na efekat selekcije. U radu su prikazane vrednosti fenotipske varijabilnosti kao i koeficijenata naslednosti i povezanosti između osobina mlečnosti analiziranih u ovom istraživanju. U radu je obuhvaćeno 1109 prvih standardnih laktacija, krava crnobele rase, potomaka 9 očeva gajenih na 7 farmi Poljoprivredne korporacije Beograd u toku 2008. godine. U istraživanju je ispitan uticaj oca grla, farme na kojoj je grlo gajeno i sezone teljenja na fenotipsko ispoljavanje i variranje osobina mlečnosti u standardnoj laktaciji. Na fenotipsku ispoljenost i varijabilnost prinosa mleka, prinosa mlečne masti i prinosa proteina u standardnoj laktaciji, visoku statističku značajnost (p lt 0,01) ispoljili su otac grla, farma i sezona teljenja. Utvrđene vrednosti koeficijenata naslednosti za prinos mleka, sadržaj mlečne masti, sadržaj proteina u mleku, prinos mlečne masti, prinos proteina iznosile su: 0.115, 0.049, 0.017, 0.119. i 0.111, retrospektivno. Vrednosti koeficijenata genetskih korelacija osobina mlečnosti iznosile su od: -0.746 (prinos mlečne masti-sadržaj proteina) do 0.983 (prinos mlečne masti-prinos proteina)
