The paper deals with adverse interactions between line stimuli ineccentric vision. Bothcontrast thresholdandjust noticeable difference of slanthave been measured for a test line as a function of the distance from a number of surrounding lines. Test lines were either parallel or perpendicular to the surrounding lines. It turns out that theinterferenceaffects both contrast threshold and j.n.d. of slant with a clear-cutorientational specificity. The surprising result is the extensive spatial range of the interference: between parallel lines it operates over retinal distances of about 0.4?t, degrees, where?t, is the eccentricity of the test line. Large-distance interference limits eccentric spatial vision in daily life much more than classic visual acuity limits would indicate, and makes eccentric vision probably quite different from "unfocussed" foveal vision.