A cross-sectional study was conducted from October 2013 to May 2014 with the objectivesrnto estimate the prevalence of ectoparasites of sheep in ectoparasites controlled andrnuncontrolled area, assess major risk factors as well as evaluate effect of ectoparasites onrnlivelihood of farmer in ectoparasites controlled and uncontrolled areas of Arsi Zone,rnOromiya Region. A total of 969 sheep (646 sheep from controlled area and 323 sheep fromrnuncontrolled area) were examined for presence of ectoparasites. Accordingly, fromrncontrolled area 371 (57.43%) and from uncontrolled area 285 (88.24%) were infested withrnone or more ectoparasites. The ectoparasites identified from controlled area were B. ovisrn48.9%, Linognathus spp 0.93%, sheep keds 7.4%, 2.32% B(R). decoloratus, 1.46% A.rnvariegatum, 1.08 % A. gemma, 4.59% R. evertsi evertsi, and 0.31% mixed tick infestationrnand 12.5% mixed infestation. The ectoparasites identified from uncontrolled area were B.rnovis 81.4%, Linognathus spp 0.9%, 1.79% B(R). decoloratus, 2.62% A. variegatum, 9.29%rnR. evertsi evertsi, 4.3% mixed tick infestation and 32.2% mixed infestation. The risk ofrnectoparasite infestation in sheep of uncontrolled area were 5.644 times higher than controlledrnarea sheep (OR=5.644, p=.000). Significantly higher prevalence of lice, tick and kedsrninfestation in the uncontrolled area than the controlled area was recorded. The risk of lice,rnkeds and tick infestations in uncontrolled area was 7.061, 3.836 and 2.074 times higher thanrncontrolled area respectively. Age and management related variation was not observed in thernprevalence of ectoparasite in both controlled and uncontrolled area. Significantly (OR=0.455,rnp=0.000) higher prevalence of overall ectoparasite infestation in the female sheep ofrncontrolled area than the male was observed. Female sheep in controlled area were 1.129rntimes at higher risk for lice infestation than male. Significantly higher prevalence of keds inrncontrolled (OR=0.081, p=0.000) and in uncontrolled area (OR=0.715, p=0.000) on woolyrnthan hairy sheep was recorded. The logistic regression results showed significant higherrnprevalence of tick infestations in female sheep (OR=1.861, p=0.000) and poor bodyrncondition sheep (OR= 0.478, p=0.015) of uncontrolled area. Female sheep and poor bodyrncondition sheep of uncontrolled area were 1.861 and 0.478 times at higher risk for tickrninfestation than male and good body condition sheep respectively. Favorable climaticrnxrnconditions, poor husbandry and animal management, lack of awareness by farmers, and weakrnanimal health extension services are believed to have contributed for widespread distributionrnand occurrences of ectoparasites. Higher prevalence of ectoparasites observed in therncontrolled area put under question the effectiveness of ectoparasites control in selectedrndistricts of Oromiya Region. The growing threat of ectoparasites to small ruminantrnproduction and the tanning industry needs well-coordinated, appropriate and urgent controlrnintervention.rnKey words: Controlled/uncontrolled, Arsi Zone, Ectoparasites, Sheep, Oromiya