The blood pressures (BP) in 418 vegetarian Seventh-day Adventist (SDA) volunteers in Western Australia were compared with those in 290 non-vegetarian volunteers in Narrogin, a Western Australian country town. The mean systolic and diastolic BPs in the SDAs, adjusted for age, sex, height and weight (128.7/76.2 mm of mercury) were significantly less than those in the Narrogin residents (139.3/84.5). It appeared unlikely that these differences could be explained by differences in alcohol, tobacco, tea, coffee or egg consumption, socioeconomic status or physical activity. There was, however, a gradient toward increasing BP with increasing egg intake in SDAs, and SDAs who drank tea or coffee had a higher mean diastolic BP than those who did not (mean difference of 4.2 mm of mercury). The possibility that selective bias or unmeasured environmental differences might explain the difference in BP between the two groups is discussed.