Experiments were carried out in stressful foot shock and noise stimulated male Sprague Dawlay rats. 3'-end digoxigenin-labeled 26 mer oligonucliotide probe was used to detect the vasopressin (AVP) mRNA in hypothalamic tissues. Dot blotting technique was used in the assessment of AVP mRNA level. The results showed that the tail systolic arterial pressure of rats increased gradually after stressful stimulations of foot shock in combination with noise. The difference in tail systolic blood pressure between control and stimulated rats was statistically significant after 5-day stimulation. By the ninth day, the systolic blood pressure of the stressed rats reached the highest level and maintained thereafter for several days. No significant difference was observed in the AVP-mRNA level between control and stressed rats by the time when stimulated for 4 days, but it significantly increases when stimulated for 6 days or longer (by the 6th day: P < 0.005; by the 15th day: P < 0.001). No difference was found in plasma osmolalities between control and stressed animals. These results indicate that the stressful foot shocks in combination with noise stimulations may cause an increase in AVP-mRNA level in the hypothalamus, which was accompanied by an increase in systolic arterial pressure. The mechanism of increase in AVP-mRNA level upon stress stimulation remains to be elucidated.