Abstract: To ascertain the harmfulness of hyperinsulinemia in patients with essential hypertension（HT）,oral glucose tolerance test（OGTT） and insulin release test（IRT） were made on 140 patients with HT.Each patient underwent cardiovascular,neurological and nephrological examination,including echocardiography,Holter′s monitoring,brain SPECT,CT,blood and urine analysis （albumin/24 h urine,creatinine clearance rate,β\-2 microglobulin）.The HT was divided into 3 groups∶group 1,HT with normal OGTT and IRT （n=27,19.3%）;group 2,HT with normal OGTT and hyperinsulinemia（HIS）（n=88,\62.8%\）;group 3,HT with impaired OGTT and HIS （n=25,\17.9%\）.Another 52 cases of HT complicated with overt NIDDM served as group 4.It was found that the occurrence rate of nephropathy and neurological diseases （hemorrahge,infarction and TIA） increased steadily from group 1 to group 4,with no difference between group 3 and 4.Despite no difference in LV mass index among the 4 groups,the occurrence rate of impaired cardiac systolic and diastolic function,frequent ventricular and atrial ectopic beats increased from group 1 to group 4.The occurrence rate of target organ damage in HT with HIS is intermediate between HT without HIS and HT complicated with overt NIDDM.In view of organ damage,HT with HIS may be a transitional syndrome from simple HT to HT complicated with NIDDM.