A population survey of 60-year-old men (n=331) was performed in Uppsala. tthe prevalence of hypertension defined as established hypertension and those having an unknown diastolic blood pressure (DBP) of greater than or equal to 105 mmHg was 19.3%. Of the hypertensive population, 35.9% had not been detected previously. In the treated group, 43.9% were poorly controlled regarding the BP level. Thus 64.1% of the total hypertensive population at the age of 60 years were either undetected or inadequately controlled. Excretion of urinary electrolytes was also evaluated in this work. All participants of the health survey except four performed a 24-hour collection of urine following the health examination. Care was taken with endogenous creatinine clearance. Negative and significant correlations were noted between excretion of sodium and potassium in urine and DBP levels in the group (n=23) of untreated hypertensives. In a population sample (n=135) of healthy subjects devoid of medical treatment in the same population survey, a positive and significant correlation was noted between the systolic BP and the urinary excretion of sodium. Thus up to a certain BP level there is a pressure diuresis and at higher BP levels the kidney retains electrolytes.