This study was designed to clarify the toxic effect of low and high doses of nickel on reproductive functions of immature rabbits treated with PMSG ,with trials to restrict the harmful effects of nickel administration Thirty seven immature female New Zealand rabbits were used for this purpose, divided into five groups .Group I, kept as control; group II, administered orally low doses of nickel (200 ug/animal) , group III, were given high doses of nickel(1000 ug/animal); group IV, were given low doses of nickel with 50 ug manganese sulphate .The treatment with nickel and/or manganese were continued for 8 weeks, five times per week Group V, not treated with PMSG and kept as control .All groups(except group V)were treated with 200 LU. pregnant mare serum gonadotrophin (PMSG) before decapitation of animals. The results showed that both nickel doses induced inhibitory effect on the ovarian activity either in the ovarian weight or in the number of growing follicles and the total ovarian response Estradiol-17B was significantly increased in both the plasma and ovarian tissues after treatment with low doses of nickel and decreased significantly in the ovarian tissue of high dose nickel group. Progesterone concentration was significantly decreased in the plasma of all treated groups and in the ovarian tissues of groups III and IV only, compared with control group. Thyroxine (T4) recorded a significant decrease in group III only .Fractionation of protein showed only elevation in gamma globulins with low dose levels of nickel, while other types of globulins were not affected. Regarding the blood picture, WBCS were affected significantly in all experimental groups, while RBCS decreased after low nickel dose treatment only A highly significant increase of nickel in the plasma and ovarian tissues in group II & II ,was recorded and manganese increased in groups III & IV Copper level was significantly decreased in both plasma and ovarian tissues in groups II and III. It is concluded that, nickel treatment inhibited the ovarian activity and disturbed the ovarian steroid hormones release and/or biosynthesis; and may have a stimulatory effect on the immune system in low doses.