Passive stretch of the heart has a direct effect on cardiomyocytes and other cell types including cardiac <em>fibroblasts</em>, endothelial cells, and vascular smooth muscle cells (VSMCs). Cardiomyocytes are targets for the action of peptide <em>growth</em> <em>factors</em> found in myocardium, suggesting an autocrine or paracrine model of the hypertrophic process. In this study we examined stretch-dependent cellular communication between cardiomyocytes, cardiac <em>fibroblasts</em>, endothelial cells, and VSMCs. Stationary cardiomyocytes were incubated with stretch-conditioned medium (CM0-CM60) derived from stretched (for 0-60 min) cardiomyocytes, cardiac <em>fibroblasts</em>, endothelial cells, and VSMCs. The expression levels of protooncogenes (as c-fos, c-jun, and fra-1) were measured, and as an indication of a hypertrophic response the expression of atrial natriuretic peptide (ANP) was measured. Stationary cardiomyocytes that have been incubated for 30 min with CM from stretched (for 0-60 min) cardiomyocytes, cardiac <em>fibroblasts</em>, endothelial cells, and VSMCs showed distinct gene expression patterns that were time-dependent and cell-type specific. In stationary cardiomyocytes, CM derived from stretched cardiomyocytes caused decreased c-fos and fra-1 expression by 37 and 20%, respectively (CM30), elevated c-jun expression by 20% (CM45-CM60), and increased ANP expression by 106% (CM45). CM derived from stretched cardiac <em>fibroblasts</em> caused increased c-fos expression by 41% (CM60), no significant changes in c-jun expression, and increased fra-1 and ANP expression by 39 and 20%, respectively (CM45). CM derived from stretched VSMCs induced an initial decrease in c-fos expression followed by an increase of 13% (CM45) and induced increased c-jun, fra-1, and ANP expression by 39, 24, and <em>22</em>%, respectively. CM15-CM60 derived from stretched endothelial cells caused decreased c-fos, c-jun and fra-1 expression by 20, 25, and 25%, respectively, and increased ANP expression by 18%. Our data indicate that gene expression of cardiomyocytes in stretched myocardium is regulated by mediators released by cardiomyocytes, cardiac <em>fibroblasts</em>, endothelial cells, and VSMCs. This observation emphasizes the involvement of nonmyocyte cells in the early stages of cardiomyocyte hypertrophy caused by cardiac stretch.