OBJECTIVE The association between job strain and ambulatory blood pressure was studied among female white-collar workers. METHODS This cross-sectional investigation studied 210 women in high- or low-strain jobs randomly selected from 3183 women of all ages, employed as white-collar workers. The women wore an ambulatory blood pressure monitor for 24 hours during a workday. Mean blood pressures were calculated. Psychological demands and decisional latitude were measured twice (14 months before and 7 days before the blood pressure measurement) with 2 scales recommended by Karasek. RESULTS Significant differences in blood pressure were found according to current job strain among the women holding a university degree. Their mean blood pressures during work were significantly higher [8.0 mm Hg (1.1 kPa) systolic and 6.4 mm Hg (0.8 kPa) diastolic blood pressure] in the high-strain group than in the low-strain group. Statistically significant elevations in blood pressure over the 24-hour period were also found for women with a university degree. Cumulative exposure to high strain over 14 months was also significantly associated with high systolic blood pressure at work, in the evening, and over a 24-hour period irrespective of other factors related to blood pressure. Among the women without a university degree, the blood pressure differences observed between the job strain groups were less than 1 mm Hg (0.1 kPa) and not statistically significant. CONCLUSIONS These results provide support for the effect of job strain on ambulatory blood pressure only among female white-collar workers holding a university degree.