The effects of calving season , parity and age at first calving on performance traits and phenotypic correlations between these traits were studied in. 587 Holstein    Friesian  cows  Mean 305- day milk yields and calving Interval were significantly affected by calving season while this effect was non-significant on daily milk yield, lactation length and dry period. Milk traits, calving interval and dry period were significantly different. The calving interval was highest in third parity  (452 days) and lowest in the first parity (404 days). The dry period was highest during 3rd lactation (161 days) and lowest in the 1st lactation (81 days). The decreasing,  in milk yield  with increasing parity suggesting that factors other than parity cows was contributing to the observed results. Age at first calving indicated that  daily milk yield and mean 305 day milk yield were highest (P <0.01) for calving at 28 to 30 months compared with cows calving at 24 to 27 months. Whereas calving interval was highest for  calving at 24 to 27 months compared with 28 to 30 month of age at first calving. Highly significant. positive phenotypic correlations of lactation length with milk yields, calving interval, 305- day yields and daily milk yield were 0.73, 0.60 0.87 and 0.23, respectively. The phenotypic correlations were found to be negative between            dry period and milk yield  (-0.30) daily yield (-0.36) and  305- day yields (-0.18). Results may imply that Holstein-Friesian cows in sub tropic are not producing up to their potential probably because of shortcomings in management and relatively   harsh climatic conditions.