The objective of this study was first to investigate the prevalence of poultry coccidiosis and tornidentify the coccidial species occurring in the study area on local strain and Rhode Island Redrnbreed chicken. The duration of the study was from September up to December, 2003 and thernsample size for local strain and RIR breed was 160 and 31 respectively. The study involvedrnquestionnaire survey, fecal examination, necropsy examination and identification of coccidialrnspecies based on their morphology, predilection site in the intestine and sporulation time.rnFrequency detection of oocyst in the fecal samples from RIR breed and local strain chickenrnwas 80.65% and 61.25% respectively. This finding indicated that coccidial infection in RIRrnbreed was significantly higher than in local strain chicken (p < 0.05). The lesion score andrnmean oocyst output per gram feces was also considerably higher in RIR breed than in localrnstrain chicken (p < 0.05, P < 0.001 respectively), which may be the difference due tornmanagement system and breed. Clinical coccidiosis occurrence in RIR breed and local strainrnchicken was 22.58% and 12.25% respectively. There was no statistically significantrndifference in clinical coccidiosis occurrence between the two genotype chickens and system.rnEimeria species identified in descending order of their occurrence were E. tenella, E.rnacervulina, E. necatrix, E. maxima and E. mitis. Mixed infections were the predominant inrnboth production systems. E. mitis was tentatively diagnosed for the first time in Ethiopia. Thernsecond study was experimental study was conducted to compare the natural resistance of localrnstrain and RIR breed chicken to acute infection with E. tenella field isolate. The resistancernwas assessed based on measuring and analysis of the parameters; oocyst production, bodyrnweight gain/loss, lesion score, packed cell volume and morbidity rate. A total of 218 chicksrnwere assigned for the experiment out of which 141 local strains and 77 RIR breed werernrandomly allocated into the experimental test and control groups. Sex difference within eachrngenotype was also taken in to account. The test groups were inoculated with 150,000rnsporulated oocysts of E. tenella per bird suspended in 1ml distilled water and given per osrndirectly in to the crop. Body weight and packed cell volume measurements were taken for allrnbirds twice, on day 0 and 8 post infection. The birds were necropsied 8 days post infection forrnlesion score. The morbidity rate in RIR breed was lower (p < 0.001) than the local strainrnchickens and no mortality during the patent period. Moreover, body weight depression in RIRrnbreed was significantly lower (P < 0.05) than the local strain chicken. However, lesion scorernand oocyst production was significantly higher than the local strain chickens (p < 0.001, p