Abstract: A total of 5093 lactation records of Holstein Friesian cows sired by 181 bulls kept at five herds in West of Turkey during the period from 1972 to 1987 were used to estimate phenotypic and genetic parameters for 305 day milk yield (305 dMY), lactation period (LP) and days open (DO). In addition, sire transmitting ability for these traits studied were also examined. Least squares analysis of variance showed significant effect of herds, season of calving, year of calving and parity on all traits studied, except the effect of season of calving on lactation period. Including age at calving as a polynomial regression of the second degree in the model yielded significant partial linear and quadratic regression of 305 dMY on age at calving, while the effect of age at calving on LP were not significant. In addition, days open had a significant effect on 305 dMY and LP. Sires within herds and cows within herds within sires were significant effect on most traits studied. Heritability estimates were 0.38 + 0.06, 0.13 + 0.03 and 0.007 + 0.02 for 305 dMY, LP and DO, respectively. All phenotypic and genetic correlations among all traits studied were positive and significant (P < 0.01), while, the genetic correlation between 305 dMY and DO was negative. Sires with at least 10 daughters were evaluated by using best linear unbiased prediction (BLUP), sire transmitting ability ranged from -717 to 601 kg for 305 dMY, from -24 to 40 d for LP and from -5 to 6 d for DO. Sires give positive and higher BLUP values for 305 dMY give positive BLUP values for LP and negative BLUP values for DO.