Prostate cancer is the second-most diagnosed and fatal carcinoma for males in the United States, and better diagnostic markers and potential therapies are needed. microRNAs are small, single-stranded RNA molecules that affect protein expression at the translational level, and dysregulation can dramatically affect cell metabolism. Comparison of 736 microRNA expression levels between the poorly metastatic SV40T immortalized prostate epithelial cell line P69 to its highly tumorigenic and metastatic subline M12 identified 231 miRs that were overexpressed and 150 miRs that showed loss of expression in the M12 cell line. Further evaluation of fourteen identified miRs was accomplished using other prostate cell lines as well as laser-capture microdissected prostate samples. Inhibition of miR-147b was found to affect proliferative, migratory and invasive capabilities of M12 cells, and reduced tumour growth in nude athymic mice. AATF, an activator of the cell-cycle inhibitor p21, was identified as a target. Overexpression of miR-9 was found to affect the epithelial to mesenchymal transition through suppression of e-cadherin, a protein characterized as lost in EMT, as well as suppression of SOCS5, an attenuator of JAK-STAT signaling. Inhibition of miR-9 resulted in reduction of migratory and invasive potential, and significant reduction of tumorigenesis and metastases in male nude athymic mice. miR-17-3p was previously identified as down-regulated in prostate cancer and loss of miR-17-3p shown to cause vimentin transcriptional activation. Reverse phase microarray analysis (RPMA) identified c-KIT as a potential second mRNA target for miR-17-3p. miR-17-3p was shown to modulate not only protein levels, but also messenger RNA levels of c-KIT. Four miR-17-3p binding sites in the c-KIT mRNA were identified. Thus, a number of microRNAs involved in prostate cancer were identified, and their targets found to be highly relevant to tumour progression and could potentially be used as targets for therapy or diagnostics. Stability of microRNAs in forensically relevant biological fluids was evaluated through heat treatment, ultraviolet radiation, and chemical treatment. The dried body fluids showed some susceptibility to harsh treatment, but in most cases microRNAs were still detectable in the samples. microRNAs could represent a highly stable species for body fluid identification methods in forensic science.