Aim: To assess the effectiveness of early diagnosis of endometriosis using polarization-phase Muller-matrix introscopy methods of scattering dehydrated films of peritoneal fluid Materials and Methods: Two groups of samples were studied: peritoneal fluid obtained during diagnostic laparoscopy – control group 3.1 - 68 samples; peritoneal fluid obtained during diagnostic laparoscopy in women with endometriosis associated with infertility – experimental group 3.2 - 59 samples. Results: By statistical analysis of a series of thesiograms of the distributions of the optical anisotropy parameters of biological preparations, the following most effective markers for the diagnosis of endometriosis by the method of polarization-phase Muller-matrix introscopy were experimentally established. Dehydrated films of peritoneal fluid:linear birefringence - unsatisfactory (– 74.6% - 80.1%) diagnostic accuracy - groups “3.1” - “3.2”; circular birefringence - excellent (– 97.6% - 98.4%) and good (– 88.1% - 88.9%) diagnostic accuracy - groups “3.1” - “3.2”; linear dichroism - good (– 90.5%) diagnostic accuracy of endometriosis - groups “3.1” - “3.2”; circular dichroism - very good (– 90.5% - 94.5%) diagnostic accuracy - groups “3.1” - “3.2 Conclusions: The conducted cycle of stusies of the diagnostic effectiveness of the new in biomedical practice method polarization-phase Muller-matrix intros copy of the polycrystalline component of biological preparations (peritoneal fluid) revealed a high level of accuracy of early diagnosis of genital endometriosis.