Potassium depletion increases and potassium supplementation decreases urinary calcium excretion. To determine whether these experimental observations have any significance in healthy free living subjects, we measured 24 h urinary calcium, sodium, potassium and serum parathyroid hormone (PTH) in 142 healthy young (aged 18-40 years) female Chinese subjects. Sodium excretion and potassium excretion were positively correlated with calcium excretion (r = 0.494, p < 0.0001 and r = 0.181, p = 0.031, respectively). However stepwise multiple regression analysis showed that only urinary sodium excretion contributed to the excretion of calcium. We conclude that in free living subjects potassium intake has little effect on calcium excretion.