The purpose of this study is to evaluate the baroreflex function using lower body negative pressure (LBNP) and neck suction in young normotensive men with or without a family history of hypertension. Twenty-two young normotensive men with a family history of hypertension (FH+) and eight young normotensive men who had no family history of hypertension (FH-) were studied. FH(+) consisted of men who had a family history of hypertension within second degree relatives. We studied cardiopulmonary baroreflex function using LBNP and carotid sinus baroreflex function using neck suction and evaluated the reflex function under stimulated conditions using both LBNP and neck suction at the same time. Systolic arterial pressure (SAP)(F = 5.42, p < 0.0001) and pulse pressure (PP)(F = 15.57, p < 0.0001) decreased similarly in both groups in response to LBNP. SAP and PP responses to LBNP were not significantly affected by the family history of hypertension. Diastolic arterial pressure (DAP) increased (F = 2.89, p < 0.005) in both groups. There was a relationship between the LBNP level and family history of hypertension (F = 2.53, p < 0.013), and the increment in DAP during LBNP -30, -40 mmHg was larger in the FH(+) group. Through mean arterial pressure (MAP) was not effected by LBNP, there LBNP level was related to the family history of hypertension (F = 2.23, p < 0.02). Heart rate increased progressively (F = 25.7, p < 0.0001) with increasing levels of LBNP; however, these changes did not differ significantly in either group.(ABSTRACT TRUNCATED AT 250 WORDS)