Background: The morphologic capillary microscopy (capillaroscopy) pattern of acrocyanosis is characterized by hemorrhages, pericapillary edema, and widened capillaries. These findings can result in a difficult differential diagnosis with systemic sclerosis (SSc). Objective: We sought to quantify the characteristics of the capillaroscopy pattern that distinguishes patients with acrocyanosis from patients with SSc and control subjects. Methods: A videomicroscope with fiberoptic illumination and personal computer–based image processing was used to measure capillary density, giant capillaries, loop width, and arterial and venous limbs in 10 patients with acrocyanosis, 10 patients with SSc, and 10 healthy control subjects. Results: Acrocyanotic patients differed in every quantitative parameter both from control subjects and patients with SSc. In particular, capillary density, which was reduced compared with that of control subjects, was much higher than that of patients with SSc: one giant capillary per finger was observed in 2 patients with acrocyanosis, whereas more than 2 giant capillaries per finger were observed in each patient with SSc. Conclusion: These differences may aid in making the distinction between the capillaroscopy patterns in acrocyanosis and SSc. (J Am Acad Dermatol 2000;42:787-90.)