IMPORTANCE Vasculopathy characterized by functional and structural abnormalities of the microcirculation plays an important role in systemic sclerosis and dermatomyositis. Although there are several advantages in using capillaroscopy, the method does not offer insight on the skin architecture, flow status, or morphology of the deeper dermal vessels. Dynamic optical coherence tomography (D-OCT) is a recently developed OCT technique that enables detection of high-speed changes in back-scattered light caused by moving cells in vessels. The high resolution of OCT enables the detection of the papillary loops. OBJECTIVE To explore the potential for OCT capillaroscopy of the nailfolds using D-OCT. DESIGN, SETTING, AND PARTICIPANTS In this case series study of 4 participants, the nailfolds in 2 patients with systemic sclerosis, 1 patient with dermatomyositis, and a healthy volunteer were scanned using D-OCT. The included patients were all outpatients from the department of dermatology at Bispebjerg Hospital. Data were analyzed from November 2015 to February 2016. MAIN OUTCOMES AND MEASURES Dynamic OCT capillaroscopy revealed a potential for imaging of the capillary morphology, the surrounding skin architecture, and flow status of the capillaries in the nailfold. Moreover, D-OCT quantified evident changes of the blood flow in normal nailfold capillaries after application of nitroglycerine and brimonidine. RESULTS This case series included 4 adult women. The quantitative measurements of the blood flow in the D-OCT images of the healthy participant showed significant quantitative differences in blood flow before and after application of nitroglycerine (mean difference, 0.035; 95% CI, 0.008-0.061; P =.02) and brimonidine (mean difference,-0.015; 95% CI,-0.082 to-0.039; P <.001). In the dermatomyositis patient, the en face D-OCT images showed a striking detailed Y-shaped dilated capillary correlating with the clinical finding. In the 2 patients with systemic sclerosis, D-OCT depicted megacapillaries, as well as loss of capillaries. Moreover, cross-sectional OCT images demonstrated a characteristic loss of distinct dermo-epidermal junction and more compact dermis with loss of adnexal structures. CONCLUSIONS AND RELEVANCE Compared with conventional capillaroscopy, D-OCT offers second-to-none information on nailfold capillary morphology, overall skin architecture, as well as quantitative data on vascular abnormalities and blood flow in the nailfold in a single scan.