Ultrasound (US) and microbubbles (MBs), as tools for gene transfection, have promising implications for gene therapy. Through permeation, US facilitates the diffusion of a gene or drug from the capillaries into the cell. Binding of the gene or drug to the MBs can further enhance the delivery efficiency, and when exposed to US, the MBs are ultimately cavitated once they have reached their target. Our goal is to create MBs that will enhance US-mediated transfection. Concerning MB production, we have shown that our prepared MBs are more concentrated, stable, and consistent than those of the leading manufacturers, via flow cytometry and Coulter Counter analysis. In in vitro experiments, we have shown that US, by itself, increases transfection efficiency (plasmid concentration in cells) of pGL3 and pGFP in human embryonic kidney 293 cells. 293 cells are transfected very readily and consistently and are therefore useful as a way to accurately quantify gene expression from transfection. Combined with MBs, transfection efficiency is further improved upon. US parameters (intensity, exposure time, frequency) and MB characteristics (concentration, size, distribution, stability) are interdependent, and thus the optimization of each parameter is important. With regards to US parameters, exposure times have been varied from 1 to 5 minutes, at intensities ranging from 0.5 to 2 watts, and the optimal condition (cells transfected minus cells killed) has been found to be 2 watts per square centimeter for 3 minutes. These conditions have been combined to quantify 293 cell gene expression. It has been shown that MBs enhance transfection rates by up to 25 times when compared to those with just US. These results have important implications in gene therapy as a means of non-invasive, localized, and efficient gene delivery.