MicroRNAs (miRNAs) are small non-coding molecules that have been shown to play key roles in regulating cellular development and to be involved in various diseases. By interfering with their target mRNAs, these molecules inhibit the expression of proteins, either by de-stabilizing the messenger RNA (mRNA) molecule or by preventing its translation. Each miRNA can target hundreds of mRNAs, and one mRNA can be targeted by several miRNAs.This makes it extremely complex to determine the regulatory functions of specific miRNAs in the transcription and translation processes. However, important advancements in microarray technology have made large scale monitoring of miRNA expression possible. This opens the possibility to move from studies of single molecules to studies of complex molecular processes, pathways, and biological systems. Recent studies have indicated important roles for miRNAs in stem cell differentiation in general and in cardiac development in particular. This paper presents a global transcriptional study where putativecorrelation between miRNA and mRNA expression in fetal- and adult heart tissues samples and in clusters of cardiomyocytes derived from human embryonic stem cells (hESCs) were investigated. Target genes of miRNAs expressed in cardiac tissue have been predicted and their transcriptional profiles investigated in tissue specimen. By using a statistical algorithm, up- and down-regulated miRNAs and mRNAs have been identified in four different cardiac related samples. In total, 17 cardiac related miRNAs have been analyzed and for each of these, clusters of negatively correlated target genes were identified. This supports the hypothesis that sets of miRNAs play an important role in modulating the expression of genes, which are important for cardiac development. Interestingly, the results from this study also indicate a global negative correlation between miRNA expression and mRNA expression, which previously has not been reported.