the method of the present invention is directed towards detecting endometriosis in a mammalian subject . this method comprises the following steps ; taking a sample from the mammal , measuring the level of sphingomyelin or phosphatidylcholine , or combinations thereof , in the sample , comparing the measured levels of sm or pc , or combinations thereof , to predetermined levels , and diagnosing the mammal based on the comparison . this method may also comprise the following steps : taking a sample from the mammal , measuring the level of f11 receptor in the sample , comparing the measured level of f11r to a predetermined level , and diagnosing the mammal based on the comparison .