A record was made of the prevalence of Cysticercus ovis in sheep and lambs killed at Albany, Waroona and Geraldton from 1970 until 1973. Detailed dissection of 292 carcases which had passed routine inspection revealed C. ovis in 60 (20.5%). A record of all C. ovis cysts found during routine boning of 102,262 carcases which passed normal inspection showed 10.4 cysts per 100 carcases, and in 6,863 carcases rejected for export because of the presence of C. ovis an average of 24.0 cysts per 100 carcases. An attempt was made to relate the incidence of carcases infected with C. ovis in a line of sheep with the incidence of undetected cysts in carcases from that line which had passed routine inspection. No relationship was established. The relative incidence of C. ovis and C. tenuicollis was recorded in 57,426 sheep to show C. ovis in 2,312 (4.0%) and C. tenuicollis in 15,123 (26.3%). Only 21 (0.1%) sheep in 26,774 were found with hydatid cysts. In 3,823 lambs from 40 farms 486 lambs from 6 farms did not show either C. ovis or C. tenuicollis and lambs from 9 farms did not show tenuicollis and lambs from 25 farms did not show C. ovis. In 604 C. ovis cysts from the hearts and diaphragms of lambs, 36 (6.0%) were considered to be alive.