Environmental factors such as animal origin, parity, year of calving and season of calving affect productivity. This work focused on the study of the effect of these factors on milk yield and reproductive traits of Friesian cows raised under Upper Egypt conditions. Data used in this investigation were collected from 1975 lactation records of pure Friesian cows raised at the station of Abnoub Alhamam belonging to the project livestock development in Assiut Governorate. The records represented 49 sires and 427 dams during the period from 1987 to 2004. Least squire means and standard errors for the studied traits were estimated using SAS 9.13. The General Linear Model (GLM) was utilized for variance analyses of milk yield and reproductive traits. Duncan's multiple range test (DMRT) was used for multiple comparisons of each trait. Animal origin constituted a significant source of variation in lactation milk yield and 305-days milk yield, while did not have any significant effect on lactation length and dry period. Season of calving had no significant effect on lactation milk yield while it has significant effect on the 305-day milk yield, lactation length and dry period. Parity effect was found to be significant on lactation milk yield, 305-day milk yield and length of lactation period, while it does not have a significant effect on the dry period. Year of calving showed significant effects on lactation milk yield, 305- day milk yield, lactation length and dry period. For reproductive traits animal origin has not had any significant effect on the lactation milk yield. Animal origin had significant effect (P<0.01) on calving interval and the age at first calving. Season of calving had significant effect (P<0.01) on days open, calving interval and age at first calving (P<0.05). All reproductive traits under study were significantly affected by year of calving. The results indicated that Friesian cows born and raised in Egypt were better in some reproductive traits, while imported cows tended to have more total milk yield.