A study was carried out of postoperative astigmatism in three groups of 50 eyes which had had cataracts removed by phacoemulsification or by planned extracapsular removal through incisions of 3.5-4 mm, 7-7.5 mm, and 10-11 mm respectively. No statistically significant differences were observed in the average number of cases of astigmatism found 100 days after the operation in the patients in whom incisions of 10-11 mm (1.82 +/- 0.95 Dp) and 7-7.5 mm (1.78 +/- 0.90 Dp) were made. Appreciable differences were discovered when these two groups were compared with cases in which small incisions had been used and who presented a lower degree of astigmatism (1.02 +/- 0.59 Dp). To ensure less postoperative astigmatism after phacoemulsification, the size of the incision should be modified as little as possible during the insertion of the intraocular lens.