Malaria at an elevation of 1 500 meters is uncommon and is usually unstable when it occurs To confirm reports of a recent increase in transmission of stable malaria in the Oksibil Valley  which is at an elevation of 1 250–1 500 meters in the Jayawijaya Mountains of Irian Jaya  Indonesia  five malariometric surveys were conducted in four villages between May 1990 and July 1991