The effect of recti tenotomy on the blood flow in iris-ciliary body was studied in 30 anaesthetized dogs with 51Cr labelled RBC of the frog as biological microspheres. The quantitative determinations showed that the blood flow in eyes with 2, 3, and 4 recti detached were 4.47%, 20.80%, and 26.15% less respectively than that of the sham-operation controls, indicating that tenotomy of more than 3 recti compromised the anterior segment circulation seriously. The development of ischemia depended on the number of vertical recti severed when the regional circulation was in a critical situation with the detachment of 2 recti.