Purpose: To investigate the survival of donor-derived epithelial cells in con ventional penetrating keratoplasty (PKP) and in homologous penetrating central l imbal keratoplasty (HPCLK). Methods and patients: Epithelial cells from 26 eyes of 26 patients were analysed. All cases were sex-mismatched (i.e. the transplan t and patient were of different genders). At suture removal more than 1 year pos t surgery, epithelial cells were obtained by gently wiping the removed sutures o n glass slides. The cell samples were analysed using fluorescent in situ hybridi zation (FISH) of the sex chromosomes. This technique makes it possible to alloca te the origin of each cell nucleus to either the donor or the recipient. Results : All 19 conventional PKPs were clear and seven had donor-derived epithelial ce lls at suture removal. Five of the seven HPCLK grafts were clear at the time of investigation (365-1355 days post surgery), and donor-derived epithelial cells were found in two grafts. Conclusion: Harvesting cells from removed sutures in combination with FISH enables the clinical study of cell survival in corneal tra nsplants without jeopardizing functioning grafts. From the limited sample invest igated, the following tentative conclusions can be made. Donor-derived epitheli al cells can remain in conventional PKP for over 1 year. In combined stem cell a nd corneal grafts (HPCLK), donor-deriv- ed epithelial cells may also be retrieved at 1 year or beyond following surger y but the correlation between their presence and a remaining clear graft is unce rtain. Purpose: To investigate the survival of donor-derived epithelial cells in con ventional penetrating keratoplasty (PKP) and in homologous penetrating central l imbal keratoplasty (HPCLK). Methods and patients: Epithelial cells from 26 eyes of 26 patients were analysed. All cases were sex-mismatched (ie the transplanted t and patient were of different genders). At suture removal more than 1 year pos t surgery, epithelial cells were obtained by gently wiping the removed sutures on glass slides. The cell samples were analysed using fluorescent in situ This technique makes it possible to allocate the origin of each cell nucleus to either the donor or the recipient. Results: All 19 conventional PKPs were clear and seven had donor-derived epithelial ce lls at suture removal. Five of the seven HPCLK grafts were clear at the time of investigation (365-1355 days post surgery), and donor-derived epithelial cells were found in two grafts. Conclusion: Harvesting cells from removed sutures in combination with FISH enables the clinical study of cell survival in corneal tra nsplants without jeopardizing functioning grafts. From the limited sample invest igated, the following tentative conclusions can be made. Donor-derived epitheli cells can remain in conventional PKP for over 1 year. In combined stem cell a nd corneal grafts (HPCLK), donor-derived-epithelial cells may also be retrieved at 1 year or beyond the surger y but the correlation between their presence and a remaining clear graft is uncence rtain.