This study was conducted in order to investigate some haematological and biochemical parameters as well as the thyroid function in pregnant cows with or without abortion and in stillborn. premature and aborted calves chronically intoxicated with nitrate in a dairy flock in Turkey. Frequent reproductive disorders (infertility, abortion, high mortality in neonates) were encountered in this flock for a one year period and the chronic nitrate poisoning was confirmed by nitrate / nitrite measurements in the food and in the drinking water. Hydrothorax and ascites were the most predominant lesions in stillborn calves and were commonly associated with lung and gastrointestinal system injuries. A total of 33.3% (3/12) hyperplasic and 66.7% (6/12) colloid thyroid goitres were evidenced in all stillborn and aborted calves. Haematological anomalies (decreases in the erythrocyte count and in the mean haemoglobin corpuscular content. increases in the haematocrit. the mean corpuscular volume and in the met-haemoglobin proportions. and the lengthening of the partial activated thromboplastin time) associated to the marked increases in plasma AST, ALP. LDH and CK activities were evidenced in pregnant cows, mainly in those with abortion, whereas the plasma vitamin A and beta-carotene concentrations were significantly depressed. In addition, the free T3 and T4 concentrations and the total T4 concentrations were significantly reduced in all pregnant cows. These results confirm that the chronic nitrate intoxication induced systemic lesions probably throughout an oxidative pathway but also alters the thyroid function in pregnant cows and in calves.