Purpose: To determine the astigmatic effect of a supero-oblique clear corneal phacoemulsification cataract incision. Setting: A university-based general ophthalmology practice. Methods: Aii eyes having supero-oblique phacoemulsification cataract surgery using the right hand of a single surgeon between April 17, 1997, and July 24, 1997, were prospectively included. There were 52 eyes of 52 consecutive patients, Manifest refraction was performed preoperatively and 1, 3, and at least 6 months postoperatively. A Fourier method of vector analysis was used. Results: Mean refractive error (Fourier corrected) for ail eyes and all ages preoperatively was -1.422 +0.085 x 35.85. At 6 months, it was -0.620 +0.190 x 14.2. There was little difference between right and left eyes. Patients older than 80 years had greater induced astigmatism. Conclusion: This study provides evidence that making a supero-oblique clear corneal phacoemulsification incision while sitting in the more natural superior position does not induce a clinically important amount of oblique astigmatism. J Cataract Refract Surg 1999; 25:949-952 (C) 1999 ASCRS and ESCRS.