A preliminary study was conducted to determine whether binocular summation (BS) in strabismic amblyopia is more decreased than in strabismus alone and whether strabismus surgery improves BS. The study included 15 strabismic amblyopes, 30 normal controls and 30 strabismic controls. Normal controls had significantly better binocular visual acuity. The mean interocular difference in visual acuity was 14±90 number of ETDRS letters for strabismic amblyopia versus 3.6±2.4 for controls and 3.8±4.2 strabismic controls. Low contrast BS was found in amblyopic and non amblyopic eyes of strabismic patients suggesting that amblyopia did not further reduce BS beyond that due to strabismus. Strabismus surgery improved low contrast BS for some patients with strabismic amblyopia indicating a further functional benefit of strabismus surgery for these patients.