Objective To evaluate the applic ation of blue-on-yellow(B/Y) perimetry in detecting the early visual field loss of glaucoma. Methods The B/Y perimetry of the G2 strategy in the OCTOPUS 101 perimetry was used to examine the visual field of 16 normal persons (32 eyes), 25 cases (35 eyes) of primary open-angle glau coma (POAG) with abnormal white-on-white (W/W) visual fields, 15 cases (15 eye s) of early POAG with normal W/W visual field, and 11 cases (22 eyes) of suspect ed POAG. Results The mean sensitivity (MS) in the normal cases, suspected POAG, early POAG, middle POAG, and late POAG was ( 23.24plusmn;1.22) dB,(20.97plusmn;3.42) dB,(18.44plusmn;3.57) dB,(11.04plusmn;1.85) dB and (8.55plusmn;2.29) dB, respectively. It was demonstrated that B/Y perimetry was more sensitive than W/W perimetry in detecting the glaucomatous visual fi eld defects,and its sensitivity was 92% and specificity was 90.62%. The averag e number of defective points in central visual field with B/Y perimetry was more than that with W/W perimetry in early and middle POAG. Conclusion B/Y perimetry is a relatively sensitive method for detection of the early visual field loss in POAG. (Chin J Ocul Fundus Dis, 2001,17:125-127)