This research was conducted to evaluate the Friesian cattle performance and study the relationship among different days open periods, total milk yield and days in milk at the first lactation of Friesian cows under different Egyptian conditions. Milk productive and reproductive data were collected from 3258 Friesian cows of six farms. Farm No.1 is a governmental, while other farms are commercial farms located in Kafr El-Sheikh, Cairo-Alexandria desert road, Gharbia, Sharqia, Daqahlia, Beheira governorates and were named from 1, 2, … to 6, respectively. Days open (DO) was classified to 10 classes, each class of 30 days (from < 60 to ≥ 300 d). The overall average of age at first calving, days open, calving interval, days in milk (DIM) and total milk yield (TMY) of all farms were 29.4 mo, 174.4, 472.0 and 359.2 d and 6173.5 kg, respectively. Results of this study showed that, in all examined farms, the 1^st lactation TMY and DIM significantly differed by the differences of the DO lengths. The study recommended that the most appropriate length of DO could be from 60 to <120 d, for Friesian cows under different managerial conditions in Egypt.