PURPOSE To assess the effectiveness of excimer laser correction of high astigmatism after keratoplasty. SETTING Kiel University Eye Hospital, Kiel, Germany. METHODS In a prospective study, we treated high astigmatism in 16 patients using a 193 nm excimer laser with a rotating mask system to make a toric ablation. Thirteen patients had postkeratoplasty astigmatism, 3, idiopathic natural astigmatism. Preoperative refractive cylinder ranged from 3.0 to 9.0 diopters (D). Minimum follow-up was 6 months. RESULTS Mean uncorrected visual acuity increased by 3.3 lines in 13 patients. Best corrected visual acuity decreased by no more than two lines in 6 patients and improved by at least one line in 6 patients. Mean cylindrical reduction was 2.8 D. Haze was classified from 0.5 to 2.0. CONCLUSIONS In this study, the excimer laser technique effectively reduced high corneal astigmatism. The main problems incurred were development of a hyperopic shift and, in some patients, an uncertain refractive outcome. Reasons for inadequate correction of postkeratoplasty astigmatism included a slightly decentered mask and irregular astigmatism from the circular scar.