The presence of high amounts of regular and irregular astigmatism after penetrating keratoplasty has been a major challenge for corneal surgeons. We have devised a technique of suture adjustment which redistributes the tension in a single continuous 10-0 nylon suture according to keratometric findings and overcomes some of the limitations of other published methods for reducing penetrating keratoplasty astigmatism. Suture adjustment is performed at the slit-lamp microscope using topical anesthesia, from as early as the first postoperative day. The effects are controllable, reversible, stable, and can achieve relaxation or tightening of any meridian. Of 330 consecutive eyes undergoing penetrating keratoplasty, 205 required and underwent one or more suture adjustments. The mean keratometric astigmatism after suture adjustment was 2.87 D (SD = 1.87), compared to a preceding consecutive series of 136 eyes without suture adjustment with 4.80 D (SD = 3.13) mean astigmatism (P less than 0.0001). This effect persisted even when the suture had to be removed (P less than 0.0001). Infection did not occur. Only five eyes (2.4%) experienced a broken suture, which was readily spliced. We recommend adjustment of a single continuous suture, when moderate to severe astigmatism is present after a penetrating keratoplasty.