Objective: To determine the repeatability and reproducibility of retinal thickness measurements with the fast macular thickness mapping protocol of Stratus optical coherence tomography. Methods: Ten eyes of 10 healthy subjects and 15 eyes of 15 diabetic patients with clinically significant macular edema (CSME) underwent 2 scanning sessions before and after pupil dilation during the same visit by 2 experienced examiners. Healthy subjects also received a third scanning session during a second visit. Repeatability and reproducibility for the foveolar center and for each of 9 Early Treatment of Diabetic Retinopathy Study (ETDRS) like regions were calculated by their repeatability and reproducibility coefficients and intraclass correlation coefficients. Results: The coefficients of repeatability were less than 8% in healthy subjects and less than 9% in patientswith diabetes and CSME. The reproducibility coefficients were less than 10% and 11% in healthy subjects and diabetic patients with CSME, respectively. There was no significant difference between scans acquired by different observers or during different visits. The intraclass correlation coefficients were always greater than 0.80 and 0.98 in healthy subjects and diabetic patients with CSME, respectively. Average± SD thickness was found to be 223± 14 and 404± 108 μ m for the central ETDRS-like region in healthy subjects and diabetic patients with CSME, respectively. Conclusion: With the fast macular thickness mapping protocol of Stratus ocular coherence tomography, our results indicate that retinal thickness measurements in dilated and undilated eyes of healthy subjects and diabetic patients with CSME are repeatable and reproducible. Objective: To determine the repeatability and reproducibility of retinal thickness measurements with the fast macular thickness mapping protocol of Stratus optical coherence tomography. Methods: Ten eyes of 10 healthy subjects and 15 eyes of 15 diabetic patients with clinically significant macular edema (CSME) underwent 2 scanning sessions before and after pupil dilation during the same visit by 2 experienced examiners. The healthy subjects also received a third scanning session during a second visit. Repeatability and reproducibility for the foveolar center and for each of 9 Early Treatment of Diabetic Retinopathy Study (ETDRS) like regions were calculated by their repeatability and reproducibility coefficients and intraclass correlation coefficients. Results: The coefficients of repeatability were less than 8% in healthy subjects and less than 9% in patients with diabetes and CSME. The reproducibility coefficients were less than 10% and 11 % in healthy subjects and diabetic patients with C SME, respectively. There was no significant difference between scans acquired by different observers or during different visits. The intraclass correlation coefficients were always greater than 0.80 and 0.98 in healthy subjects and diabetic patients with CSME, respectively. Average ± SD thickness was found to be 223 ± 14 and 404 ± 108 μm for the central ETDRS-like region in healthy subjects and diabetic patients with CSME, respectively. Conclusion: With the fast macular thickness mapping protocol of Stratus ocular coherence tomography, our results indicate that retinal thickness measurements in dilated and undilated eyes of healthy subjects and diabetic patients with CSME are repeatable and reproducible.