The association between low birth weight (LBW) and elevated blood pressure has been attributed to disturbances in the endocrine and sympathetic nervous system. The present study focussed on parameters of cardiovascular and sympathetic function and on adrenocortical activity in 24 healthy subjects aged 20 - 30 years with a birth weight of less than 2500 g at term and a control group of 24 subjects with a normal birth weight (NBW; 3200 - 3700 g) who were thoroughly matched for gender, body mass index (BMI), and age. Blood pressure, heart rate, and insulin resistance (calculated according to the homeostasis model assessment) were determined. Additionally, free salivary cortisol was measured at 08 : 00 am and 11 : 00 pm. In 13 subjects of each group, muscle sympathetic nerve activity (MSNA) was measured microneurographically at rest and after baroreflex stimulation by nitroprusside (12 NBW and 9 LBW subjects). Metabolic parameters, blood pressure, and salivary cortisol did not differ between LBW and NBW subjects. MSNA was significantly lower in the LBW group. In both groups insulin resistance correlated positively with BMI and negatively with morning cortisol. In the LBW group, but not the NBW group, systolic and diastolic blood pressure correlated positively with BMI and insulin resistance, and negatively with morning salivary cortisol. A correlation between morning salivary cortisol and the MSNA was only found in NBW subjects. This positive correlation strengthened when MSNA was stimulated by nitroprusside administration. However, in the same maneuvre a negative correlation between morning salivary cortisol and MSNA was observed in the LBW group. The data indicate that insulin resistance depends on the same factors in LBW and NBW subjects. In LBW subjects the interplay between adrenocortical and sympathetic activity is altered. Furthermore, LBW subjects differ from the NBW group in their significant interrelationship between blood pressure and metabolic factors.