A group of 1592 male Croatian soldiers (average age 32 +/- 9, ranging from 19 to 54) were examined by an internist at the war hospital. Elevated blood pressure was found in 80 men (5%); 61 of them had no history of hypertension (Group A), while in 19 patients hypertensive disease had been diagnosed before (Group B). In group A, systolic blood pressure (BPS in mm Hg), diastolic blood pressure (BPD in mm Hg) and heart rate (HR) were 182 +/- 13, 111 +/- 10, and 115 +/- 9; in group B, the values were 184 +/- 12, 108 +/- 8, 85 +/- 11. Electrocardiograms (ECG) and thorax roentgenograms of group A did not reveal any hypertension-caused signs, neither did the examination of the fundus, nor the serum creatinine values yield any abnormal results. The ECG test showed sinus tachycardia (heart rate > 100/min) but an otherwise normal function in group A. In group B, at least one of the laboratory examinations confirmed the previously diagnosed hypertension. Group A was treated with the cardioselective beta-blocker Atenolol (100 mg daily), while in group B, the previous antihypertensive medication was modified and/or increased. All patients were sent back to the front-line. Three days later, blood pressure and heart rate in group A were: BPS 139 +/- 9, BPD 87 +/- 6 and HR 77 +/- 8; and in group B: 156 +/- 11, 95 +/- 8, 75 +/- 7. A significant decrease in systolic and diastolic blood pressure (p < 0.0001) was found in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)