The prevalence of hypertension and the relationship between blood pressure, age, body mass index (BMI) and urinary cations from casual urine specimens were examined in 1,513 Chinese employees of a public utility company and non-medical personnel of a district hospital. The prevalence of hypertension, defined as systolic blood pressure greater than or equal to 140 or a diastolic blood pressure greater than or equal to 90 mmHg, or a past history of hypertension, was 17% in men and 5% in women. After excluding subjects who were on antihypertensive medication, age, body mass index, and urinary sodium/potassium ratio were independently and positively associated with blood pressure, while urinary potassium/creatinine ratio was inversely related to blood pressure. No association with urinary sodium or sodium/creatinine ratio was found. Higher mean blood pressure in men was accompanied by lower urinary potassium/creatinine and potassium concentration and higher sodium/potassium ratio, even though men had the same mean BMI when compared with women. A difference in potassium intake between the sexes may partly account for this finding. We conclude that in this Chinese population, whose dietary intake is more influenced by the West compared with Chinese in the Peoples' Republic of China, age and BMI are important determinants of blood pressure, together with potassium intake as reflected by urinary potassium excretion. No association of blood pressure with sodium excretion was demonstrated.