MicroRNAs (miRNAs) are a relatively newly discovered class of small endogenous non coding RNA molecules with important roles in cell function and cancer development. Mature miRNAs bind to complementary sequences of transcripts and either cleave or inhibit translation of the mRNA. Some studies have indicated that grouping of tumor samples based on miRNA expression profiling correlate better than mRNA expression with cell differentiation and development. Experiments with diagnostic profiling using miRNAs have lead to suggestions for the use of miRNAs in cancer therapy. The properties of the binding between the target mRNA sequence and the miRNA however, are complicated and diverse and available computer programs designed to predict miRNA targets uses different algorithms and often disagrees in their predictions. This emphasizes the need for experimental verification of putative binding sites, predicted by such algorithms. The aim of this thesis was to construct a vector system for functional miRNA target verification with EGFP as the reporter gene. Flow cytometry was chosen as the method for analysing the EGFP expression of transfected cells. The results verified the construction of five vectors: the constructed pmiRPG and four constructs with the 3’UTR sequence from KRAS, WWOX, CXXC4 and WDR79 inserted in a fusion transcript with the EGFP gene. The results presented may indicate that a promoter exchange from a phosphoglycerate (PGK) promoter to a stronger promoter could enhance the fluorescence intensity of transfected cells and give better recordings. The flow cytometry analysis in the current thesis may indicate that the miRNA hsa-let-7a regulates the KRAS gene and that hsa-miR-487 regulates the WWOX gene. However an optimalization of the miRNA target verification system should be performed before a firm conclusion can be made concerning this putative miRNA-based regulation.