Objective\ To study the prevalence of isolated systolic hypertension(ISH) of the elderly in Yunnan province.\ \ Methods\ Strictly according to the protocol of national sampling investigation of hypertension in 1991,using randomized multistage and cluster sampling method,39 283 peop le aged 15 and over in 5 cities and 5 villages were investigated for ISH.It included 18 068 men and 21 215 women,19 688 in urban and 19 595 in rural population.The definition of ISH is SBP≥21 3kPa and DBP