Purpose: To compare the reliability of the perimetry results of the first eye and the second eye with frequency doubling technology (FDT). Methods: The subjects were 328 residents who underwent the C- 20- 5 mode of FDT at a city in central Japan. FDT perimetry was always performed first in the right eye and then in the left eye without any time between tests. When more than 33% fixation loss or false-positive error was detected, the result was judged unreliable. Results: Of the 328 subjects, the bilateral perimetry results were reliable in 255 subjects (77.7% ), the unilateral results were reliable in 57 (17.4% ), and there was not a reliable result in either eye in 16 (4.9% ) subjects. Of the 57 subjects whose unilateral result was unreliable, the result of the second eye was unreliable in 50 (88% ) subjects, and the result of the first eye was unreliable in 7 (12% ). This difference in the reliability between the first eye and second eye was significant (P< 0.001). There were no differences in the age, sex, visual acuity, refractive error, test duration, or number of glaucoma suspects between the two groups whose unilateral result was unreliable in the first eye or the second eye. Conclusions: The FDT perimetry result of the second eye was less reliable than that of the first eye. Purpose: To compare the reliability of the perimetry results of the first eye and the second eye with frequency doubling technology (FDT). Methods: The subjects were 328 residents who underwent the C- 20-5 mode of FDT at a city in central Japan FDT perimetry was always performed first in the right eye and then in the left eye without any time between tests. When: more than 33% fixation loss or false-positive error was detected, the result was judged unreliable. Results: Of the 328 subjects , the bilateral perimetry results were reliable in 255 subjects (77.7%), the unilateral results were reliable in 57 (17.4%), and there was not a reliable result in either eye in 16 (4.9%) subjects. Of the 57 subjects unilateral result was unreliable, the result of the second eye was unreliable in 50 (88%) subjects, and the result of the first eye was unreliable in 7 (12%). This difference in the reliability between the first eye and second eye was significant (P <0.001). There were no diff erences in the age, sex, visual acuity, refractive error, test duration, or number of glaucoma suspects between the two groups whose unilateral result was unreliable in the first eye or the second eye. Conclusions: The FDT perimetry result of the second eye was less reliable than that of the first eye.