The objective of this study was to determine how the concentration of milk urea (MU) and FPCM production affect reproduction in Holstein dairy herds. A study comprising analyses of individual cow records from monthly dairy herd improvement milk tests including MU concentration was conducted. The effect of MU concentration on the probability of conception at first service was not significant. The results indicated a nonlinear relationship between MU concentration and the probability of conception. A significant effect of the length of calving to first service interval and FPCM was determined. The cows with the calving to first service interval longer than 2 months had by 10 % higher probability of conception. In the group with the highest FPCM a markedly lower level of successful pregnancy was determined significantly differing from the group with average FPCM production. The probability of conception at first service in the group with the lowest FPCM was at an average level.