The studies were conducted in the years 1995-2002. The experimental material were Jersey cows imported from Denmark, and their progeny born and raised in Poland. Two herds were evaluated – herd A in Jonkowo and herd B in Bogaczewo. The manyyears' opinion of chosen of usable coefficients was the aim of investigations. The parameters of reproduction and productivity were estimated imported from Danii of cattle of race Jersey in conditions of Warmia and Mazury (NE Poland) province. It was found that cow fertility was good; its decrease was noted only after five calvings. An increase in milk yield and yields of its major components was observed until the fifth lactation. In the first lactation the highest productivity was reported for herd B - 3715 kg milk, 215.61 kg milk fat (5.78%) and 139.54 kg milk protein (3.76%). In the fifth lactation the highest productivity was noted in herd A: 5275 kg, 331.59 kg (6.30%) and 214.38 kg (4.04%) respectively. The cows born and raised in Poland (generation P) were characterized by higher productivity than those imported from Denmark. The highest statistically significant difference (p ≤ 0,01), i.e. 468 kg milk, 47.99 kg milk fat and 25.57 kg milk protein, was found in the first lactation. Analysis of six successive lactations shows that Jersey cattle imported from Denmark easily adapted to the conditions of north-eastern Poland.

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