The effects of venepuncture or orchidectomy were studied, performed immediately after birth, on body weight, adrenocortical function, and some indicators of the metabolism in piglets, particularly at weaning at an age of four weeks and a fortnight afterwards. Neither venepuncture, causing the loss of ca. 7% of the total volume of blood, nor castration of the young boars exerted any adverse effect on the growth of piglets, which was rather stimulated during the sucking period in the first test. No significant differences between the experimental and control groups were found in adrenocortical activity and in the concentration of the total protein, urea, glucose, non-esterified fatty acids and cholesterol in blood plasma. The level of plasma 11-hydroxycorticosteroids showed a marked drop already a week after piglet weaning from the sow. The results are evaluated in view of potential subsequent implications of the neonatal stimulation of stress character. It was derived that neither the specific nor non-specific effects of the neonatal stress had adverse implications for piglets if the noxious dose was not beyond the adaptation and regulation abilities of the young organism.