Endonasal dacrocystorhinostomy (DCR) has gained interest in the last decade. Especially when a novice surgeon is performing the surgery, difficulty in identification of the lacrimal apparatus may complicate the procedure. We investigated the efficacy of methylene blue (MB) solution as a marker for lacrimal sac (LS) in endoscopic DCR. A total of 24 endoscopic DCR cases were performed (16 primary and 8 revision cases). During surgery, LS was irrigated with MB solution. Following lacrimal bone removal, medial wall of the LS is seen with a bluish hue. When the sac is dissected, the epithelium of the LS, which is heavily stained with MB contrasts with the surrounding nasal mucosa and therefore tailoring of the extent of the LS mucosa removal is facilitated. The follow-up period of the patients was 23 +/- 7.5 months. Of the 24 cases operated, only one case needed a re-operation. Use of MB solution is effective in both identifying LS and distinguishing it from surrounding nasal mucosa in DCR.