Clinical observation has lead us to speculate that there may be a relationship between peripheral corneal compression staining and contact lens wearing schedule (daily wear vs extended wear). We would also like to determine the clinical significance of such staining, particularly, its role as a risk factor for infiltrative keratitis. We are in the process of recruiting patients for a long-term prospective study. To date we have enlisted 102 consecutive hydrogel lens wearers and have noted the prevalence of compression staining. The prevalence of compression staining in extended wearers (59%) is twice that of daily wearers (30%). One factor ANOVA reveals a significant relationship between compression staining and wear schedule (F = 8.81, p = 0.004). This effect does not appear to be attributable to lens material or manufacturer. We also found that 5 of 43 patients with compression staining had microcysts compared with 1 of 59 non-staining wearers. Neither age nor refractive error were not found to be significant factors in staining or microcyst formation. We are continuing to recruit more patients. The casual relationship between this increased staining in extended wear and the higher incidence of infiltrative keratitis in extended wear remains an interesting avenue of exploration.