hhlim is a new heart-related gene cloned from human embryonic heart whose product participates in transcriptional regulation and cell development as a kind of transcriptional factor. Over expression of hhlim gene using a recombinant plasmid was sufficient to induce a greater than 2.49 fold increase in cardiac myocyte area compared with that untransfected with hhlim. RT-PCR and Western blot testified that transfection of hhlim into the cardiac myocyte could induce skeletal α-actin over expression and trigger the expression of embryonic related gene-BNP, which is related to the cardiac hypertrophy. Antisense hhlim expression plasmid was constructed for analyze of hypertrophy in cultured neonatal cardiomyocytes. Endothelin-1 can induce cardiomyocyte hypertrophy. Cardiac myocyte treated by ET-1 was transfected with antisense hhlim palsmid. Western blot and RT-PCR analysis demonstraned that antisense hhlim restrained the increased cell surface area induced by ET-1, or increases expression of α-actin and BNP. Individual expression vectors for hhlim, Nkx2.5 and GATA-4 could enhance BNP reporter gene expression in cardiac myocytes. Cotransfection of hhlim and Nkx2.5 produced additive luciferase expression. The results demonstrate that hhlim protein is capable of initiating the hypertrophic response in cultured cardiac myocyte by activing BNP gene expression directly and indirectly.