In a prospective study we used the change in central and peripheral (12 o'clock position) corneal thickness after two cataract surgery techniques as a parameter of tissue trauma. We looked at whether our findings indicated a difference in corneal thickness in the two groups and thus, as postulated in the literature, in the prospective endothelial cell loss. In 32 eyes (Group A) we performed small incision surgery (3.5 mm to 4.0 mm scleral-step incision) with hydrogel intraocular lenses implanted in the bag. In 30 eyes (Group B) we performed a 7.0 mm scleral-step incision with in-the-bag implantation of conventional poly(methyl methacrylate) intraocular lenses. Increases in corneal thickness (centrally and peripherally) were correlated after different postoperative periods. After 48 hours Group B showed a slightly higher increase in corneal thickness than Group A. Similar findings were observed at five days. In Group B the peripheral thickness did not show as high an increase as the central thickness after 48 hours. In all other cases the peripheral thickness increased more than the central thickness. After one month all eyes regained their preoperative thickness. We did not find a statistically significant difference in central and peripheral corneal thickness between the two groups. The results show that neither of the two surgical techniques greatly influenced the increase in corneal thickness and, consequently, the prospective endothelial cell loss.