The present study was conducted to investigate the prevalence of Eimeria infection according to anti-coccidiosis drugs treatment in 1,300 slaughtered chickens from 130 farms in Gyeongnam, Jeonnam, Jeonbuk, Gyeongbuk and Chungnam during the period from October 2002 to August 2003. The prevalence of Eimeria infection by drug administration for treatment and prevention or non-administration was shown $71.4\%,;82.6\%;and;72.3\%$, respectively, and so infection rate of chicken farms was similar independent on drug administration or not. The prevalence of Oocysts infection level of chicken farms by administrated drug for treatment was shown lower $(25.3\%)$ than for prevention $(35.4\%)$ and non-treatment $(36.2\%)$. The prevalence of Oocysts infection level by drug administration under 2 days for treatment was shown higher infection rate $(32.2\%)$ than over 3 days $(20\%)$ and also under 2 days for prevention has similar tendency of that of treatment and so, it was conclusion that administration of drug over 3 days has the effect for treatment and prevention of Eimeria infection. The prevalence of Oocysts infection level by age for prevention has various level from $48.8\%;to;22.9\%$ but on $22~25$ days was shown the most higher ratio $(48.8\%)$ and on $19~21$ days was shown the lowest rate $(22.9\%)$ among the all age groups.