The impact of birth weight and gestational age on blood pressure in adult life was studied in a population of 49-year-old men born in 1926-27 who took part in a screening investigation of blood pressure performed in 1975-76 in Göteborg, Sweden. Birth records were traced in 430 subjects and compared with screening records. The adult systolic blood pressure (SBP) was not correlated with birth weight but was inversely correlated with gestational age in the whole study group (r = -0.10, P = .04; n = 430). The correlation between adult blood pressure and gestational age was stronger in preterm subjects, ie, those with a gestational age less than 38 weeks (for SBP, r = -0.46, P = .001 and for diastolic blood pressure [DBP], r = -0.44, P = .01; n = 44), and these correlations were independent of birth weight. There was, however, no correlation between adult blood pressure and gestational age in subjects born at term (between 38 and 41 complete weeks of gestation) or postterm (more than 42 weeks of gestation). The inverse correlation between adult SBP and gestational age was stronger in low-birth-weight subjects (< or = 2500 g; r = -0.86, P < .001; n = 14). After adjustment for birth weight, in this group an increase by 1 week of gestation was associated with a decrease in adult SBP of 7.2 mm Hg (95% CI, 10.1-4.2). In the whole study group, a positive correlation was found between adult blood pressure and adult body mass index (BMI) (r = 0.30, P < .001 for SBP and r = 0.33, P < .001 for DBP). In preterm subjects, however, no such correlation was found, but in subjects born at term or postterm, adult blood pressure was significantly correlated with BMI (for SBP at term, r = 0.34, P < .001 and postterm, r = 0.47, P < .001 and for DBP at term, r = 0.36, P < .001 and postterm, r = 0.30, P < .05). This study indicates that adult blood pressure appears to be related to different variables in different ranges of gestation. In preterm subjects, gestational age appears to have a great impact on adult blood pressure. In subjects born at term or later, however, adult blood pressure was not associated with factors related to birth, but only to the adult BMI.