In this study, we used reverse transcriptase-polymerase chain reaction (RT-PCR) to compare the expression of mRNAs encoding endothelin-1 (ET-1), endothelin receptors type A (ETA-R) and type B (ETB-R) and ET-1-degrading enzyme neutral endopeptidase 24.11 (NEP) in 15 endometrial cancer tissues and 13 normal endometrial tissues. The relative levels of ET-1 mRNA in endometrial cancer tissues did not differ from those in normal endometrium. Both ETA-R and ETB-R mRNA levels were significantly lower in endometrial cancer tissue than in normal endometrium (P < 0.001). The complete lack of NEP mRNA in endometrial cancer tissues was in marked contrast to results from normal endometrium (P < 0.001). In conclusion, differential expression of mRNAs encoding ET-R and NEP in normal endometrium and endometrial cancer suggests that ET action is altered in endometrial cancer compared with normal endometrium.