Visual　illusions　emerge　as　an　attractive　field　of　research　with　the　discovery　over　the　last　century　of　a　variety　of　deep　and　mysterious　mechanisms　of　visual　information　processing　in　the　human　visual　system.　Among　many　classes　of　visual　illusion　relating　to　shape,　brightness,　colour　and　motion,　＇geometrical　illusions＇　are　essentially　based　on　the　misperception　of　orientation,　size,　and　position.　The　main　focus　of　this　paper　is　on　illusions　of　orientation,　sometimes　referred　to　as　＇tilt　illusions＇,　where　parallel　lines　appear　not　to　be　parallel,　a　straight　line　is　perceived　as　a　curved　line,　or　angles　where　lines　intersect　appear　larger　or　smaller.　Although　some　low　level　and　high　level　explanations　have　been　proposed　for　geometrical　tilt　illusions,　a　systematic　explanation　based　on　model　predictions　of　both　illusion　magnitude　and　local　tilt　direction　is　still　an　open　issue.　Here　a　neurophysiological　model　is　expounded　based　on　Difference　of　Gaussians　implementing　a　classical　receptive　field　model　of　retinal　processing　that　predicts　tilt　illusion　effects.