Although it had been widely accepted that vitreous traction plays a key role in the pathogenesis of aphakic cystoid macular edema, vitreoretinal traction is not observable in many patients and other hypotheses have also been investigated. The authors review the present knowledge of the anatomy of the vitreoretinal interface and the pathologic findings in cystoid macular edema. A new hypothesis combining the effects of both traction and inflammation is proposed.