Abstract: The present invention provides a method of diagnosing endometriosis and/or infertility in a subject, comprising: a) obtaining a sample from the subject; b) detecting a level of expression of a SIRT1 gene and/or protein in the sample; c) detecting a level of expression of a BCL6 gene and/or protein in the sample; d) comparing the level of expression detected in (b) with the level of expression of a SIRT1 gene and/or protein in a sample obtained from a control subject or a population of control subjects; e) comparing the level of expression detected in (c) with the level of expression of a BCL6 gene and/or protein in a sample obtained from a control subject or a population of control subjects; and f) diagnosing the subject as having infertility when the subject has a level of expression of the SIRT1 gene and/or protein greater than the level of expression of the SIRT1 gene and/or protein of the control subject or population of control subjects and also has a level of expression of the BCL6 gene and/or protein t