Abstract: The effect of diethylcarbamazine (DEC)-medicated salt as a single measure on the) control of bancroftian filariasis in Zhecheng County, Henan Province in 1978 was reported. 9,422 subjects were selected from 8 production brigades from all parts of the county, having had blood examination before and after medication. The total dosage for each person was 9g of diethylcarbamazine. At the end of treatment the positive rate of mi-crofilaremia reduced from 6.25% to 0.2%. One year after, 7,485 subjects from 6 brigades were examined, the positive rate was 0.39%. 3 years later,?7 914 subjects from 8 brigades were examined, and the positive rate was 0.69%. The figures had come up to the parameter of filariasis control stipulated by the state (the positive rate of microfilaremia below 1% in all the production brigades). By the end of the medication, of 313 subjects with microfilaremia examined before, 97.1% of patients were cured, the density of mi-crofilariae was reduced from 11.96/60mm3 to 1.33/60mm3.