Background and Objectives Endometriumablation provides an alternative treatment modality to hysterectomy for dysfunctional uterine bleeding (DUB). Its feasibility was demonstrated in animal studies. The purpose of this study was the evaluation of histological changes following photodynamic endometrial ablation in patients. Study Design/Materials and Methods 5-Aminolevulinic acid (ALA) was topically applied in three premenopausal and one postmenopausal patient 4–6 hours before laser-illumination. ALA-concentration: 100–400 g/ml, NaOH-titration (pH 5.5). Volume applied, 1.5–2.0 ml; intrauterine balloon-lightdiffuser; wavelength, 635 nm; lightdose, 160 J/cm2. Hysterectomy was performed 3–152 days after photodynamic ablation. Histological examination was carried out on endometrium sections stained with hematoxylin and eosin (H&E). Results Necrosis including the full thickness of the endometrium was found 3 days after photodynamic endometrial ablation. Specimens collected after 35 and 152 days did not exhibit fibrosis or adhesions. Foci of preserved endometrium were detected in all patients. Conclusions Photodynamic endometrial ablation is selective and does not cause endometrial fibrosis or adhesions. Lasers Surg. Med. 32:305–309, 2003. © 2003 Wiley-Liss, Inc.