PURPOSE. To evaluate clinical outcome of cataract surgery under systemic anticoagulant therapy using coumarin. METHODS. This clinical interventional comparative nonrandomized study included 441 patients (441 eyes) consecutively undergoing standard phacoemulsification with clear cornea incision and topical anesthesia. The study group consisted of 21 (4.8%) patients for whom systemic coumarin therapy was continued despite surgery. The control group included 420 patients without anticoagulant coumarin therapy prior to surgery. Study group and control group did not vary significantly in age, preoperative visual acuity, axial length, refractive error, preoperative intraocular pressure, or surgeon. RESULTS. Frequency of intraoperative or postoperative hemorrhages, intraoperative complications such as posterior capsule rupture, postoperative visual acuity, and intraocular pressure did no vary significantly (p > 0.30) between study group and control group. CONCLUSIONS. For patients under systemic coumarin therapy, the rate of surgical complications may not markedly be increased compared to patients without coumarin therapy, when standard phacoemulsification with clear cornea incisions is performed with topical anesthesia. Systemic coumarin therapy does not have to be stopped prior to cataract surgery.