Abstract: Bancroftian filariasis used to be highly prevalent in Shandong Province, involving 74 counties or cities. According to the estimation made in 1950s, there were about 2.5 millions of microfilariaemia cases and an equal number of patients with different clinical manifestations of filariasis. Mass survey and treatment of microfilaremia cases were carried out during the years from 1958 to 1960 in the most heavily endemic areas in the southern part of the province, resulting in a reduction of about 50% of the microfilarial rate. A province-wide control programme commenced in 1970 and about 59 million blood examinations were made. Altogether 1,813,596 microfilaremia cases were detected and treated with 2-3 regular courses of hetrazan (DEC). In 27 highly infected counties, the average microfilarial rate reduced from 1.3% to 0.09% after 2-7 mass blood surveys and selective treatment. Mass treatment with one regular course of DEC was given to all the people over 5 years of age in some communes and villages of 14 moderately infected counties where the microfilarial rate was still above 1% after 2-5 mass surveys and treatment. The average microfilarial rate was thus brought down to 0.17% as compared with 5.8% before control measures were taken. In 33 highly infected counties, DEC-medicated salt was given to a total population of about 23 million people for 4-6 months following 2-3 successive mass blood surveys and treatment. As a result, the average microfilarial rate has dropped from 12.4% in 1970 to 0.15% in 1980. Through these measures, the overall microfilarial rate in the province was reduced from 4.6% to 0.1% in 1983. In 74.8% of the 4,735 villages examined, no more microfilaremia cases could be found and the microfilarial rate in the remaining villages was less than 1%. The natural infection rate of Culex pipiens pollens, the main mosquito vector, has been reduced to almost zero, while in 1950s it was as high as 37.5-51.9%. Meanwhile, no new infection occurs in children born after the anti-filariasis campaign.It has been found that for blood survey and evaluation of control measures, the routine two-film method with 120 mm3 of blood taken from the earlobe is as reliable as the membrane filtration technique with 1 ml of venous blood but is much more simple and practicable. Patients with elephantiasis are effectively treated with intramuscular injections of aqueous extracts of mulberry leaves or audiofrequency electrotherapy in combination with bandage. Renal pelvic lavage with 1 % silver nitrate has been used for the treatment of chyluria with an immediate cure rate of 82.2% and 70% of cases remain symptomless 3 years after the treatment.For surveillance after the control of filariasis, the remaining microfilaremia cases could be traced by blood examination of the people in the houses or villages where naturally infected mosquitoes are discovered. This method may be used for identifying the residual source of infection instead of mass blood surveys.