It is the aim of this study to test the hypothesis that also mRNA levels are down-regulated in dilated cardiomyopathy. beta 1 and beta 2 adrenoceptor ligand activities and mRNA expressions were analyzed in left ventricular biopsies from six organ donor hearts, in papillary muscles from seven patients operated on for mitral regurgitation, and in six explanted hearts as the result of dilated cardiomyophathy. mRNA levels were determined by solution hybridization. beta 1 ligand activity was decreased in the cases of mitral regurgitation (p < 0.01) and dilated cardiomyopathy (p < 0.001). beta 2 ligand activity did not differ between the three groups. mRNA expression was depressed in mitral regurgitation regarding both beta 1 (p < 0.001) and beta 2 (p < 0.01), while no differences were observed in dilated cardiomyopathy as compared to the donor hearts.