Abstract: This survey was conducted in cooperation with local institutions in 7 provinces and 1 autonomous region during 1979-1984.The in vitro microtechnique was conducted according to the instruction for use of the microtest kit supplied by WHO. WHO extended test in vivo was also used. The patients were kept in hospital for at least 8 days and followed up for 4 weeks.Of 90 cases from 4 counties in Hainan Island tested in vivo, 74 were resistant (82.2%). Of 155 cases from Yunnan, 115 were resistant(74.2%). Of 37 cases tested in Lingyun and Tiandong Counties of southwestern Guangxi, 32.4% were resistant. Of 31 cases tested in Wangmo, Libo and Shandu Counties of Southern Guizhou, 6.5% were resistant. All the 20 cases tested in Laian and Shucheng Counties of central Anhui were resistant. Of 52 cases tested from Henan, 5.8% were resistant. Of 2 cases tested in Chongan County of northern Fujian, one was resistant. No resistance was found in 8 cases tested in western Jiangsu.By using in vitro test, of 120 cases tested in Hainan Island, 94.2% showed resistance. Of 88 cases tested in Yunnan, 85.2% were resistant. Of 27 cases in Guangxi, 77.8% showed resistance. In Guizhou 36.4% of 33 cases were resistant. In Anhui all the 22 cases tested were resistant. Of 9 cases in Henan, 33.3% were resistant. Of 12 cases in Jiangsu, 41.7% were resistant. The drug resulted in 99.9% schizont inhibition (EC 99.9) at the level of 29.5×10-6M/L in Hainan Island, 85.7×10-6M/L in Yunnan, 13.8×10-6M/L in Guangxi, 3.1×10-6M/L in Guizhou, 2.2×10-6M/L in Henan, 18.6×10-6M/L in Anhui, 3.5×10-6M/L in Jiangsu.This study demonstrated that chloroquine resistance was present in Hainan Island and southern Yunnan and the extent of resistance was rather high. In southwestern Guangxi and central Anhui chloroquine resistance has also been detected but its degree is lower. In Henan, southern Guizhou and Jiangsu chloroquine resistance is incipient.