In a recent review, Rossi et al. [1] considered interactions between endothelin-1 and the renin angioten-sinaldosterone systems, and cited our work [2,3] on the super-additive vasodilator and hypotensive effects of the non-selective endothelin receptor antagonist, SB 209670, and losartan in hypertensive male, heterozygous, transgenic ((mRen-2)27) rats. In these animals we observed clear effects of SB 209670 alone, and discussed reasons why endothelin should be involved in what was, nominally, a model of hypertension created by manipulation of the renin-angiotensin system. Unfortunately, Rossi et al. [1], while citing our work, seem not to have understood that we investigated male, heterozygous transgenic rats and also found an effect of endothelin receptor antagonism alone, because they conclude that, in this model of hypertension, endothelin does not play any major role! So, while we are grateful for the citations, we feel that the conclusions reached by Rossi et al. [1] should be more guarded, since the only published work [4] which conflicts with our findings used a different endothelin receptor antagonist and a different source of Sprague Dawley rats for the heterozygous cross (Edinburgh vs. Hannover). Perhaps, therefore, the area is still open for investigation.