PURPOSE: The aim of the study is to evaluate the retinal and choroidal microvascular changes via optical coherence tomography angiography in patients who received hydroxy-chloroquine. METHODS: In total, 28 eyes of 28 patients (24 females, and 4 males) receiving treatment with hydroxy-chloroquine were assessed in this cross-sectional cohort study (hydroxychloroquine group). The high-and low-risk groups consisted of patients receiving hydroxychloroquine for ≥5 years (14 eyes of 28 patients) and <5 years (14 eyes of 28 patients), respectively. A total of 28 age- and gender-matched volunteers were enrolled as the control group. The macular flow area (superficial, deep, and choriocapillaris), superficial and deep vessel density, foveal avascular zone area, central foveal thickness, and subfoveal choroidal thickness parameters were measured by optical coherence tomography angiography. RESULTS: The mean age of the 28 patients who received hydroxychloroquine and the 28 age-matched controls was 45.5 ± 11.1 years (range: 29-70 years) and 44.5 ± 13.9 years (range: 28-70 years), respectively. In patients who received hydroxychloroquine, the values for the superficial, deep, and choriocapillaris macular flow areas were 13.578 ± 0.30, 13.196 ± 0.31, and 17.617 ± 0.42, respectively. In controls, these values were 16.407 ± 0.95, 13.857 ± 0.31, and 18.975 ± 0.76, respectively (p<0.05 for all). The superficial, deep, and cho-riocapillaris flow areas were significantly smaller in patients who received hydroxychloroquine than those in controls (p<0.05 for all). Superficial and deep vessel densities were significantly reduced in patients who received hydroxychlo-roquine in all regions (i.e., foveal, parafoveal, temporal, superior, nasal, and inferior) (p<0.05 for all). Moreover, significant difference was observed between the groups in the foveal avascular zone area (superficial and deep), central foveal thickness, and subfoveal choroidal thickness (p<0.05 for all). CONCLUSIONS: Retinochoroidal microvascular flow and vessel density of the macular area were significantly decreased in patients who received hydroxychloroquine. Hy-droxychloroquine may damage the retinochoroidal mi-cro-vascular architecture. Optical coherence tomography angiography may contribute to the early detection of hy-dro-xychloroquine-induced retinal toxicity.