Ultrasonically stimulated microbubbles can enhance the localized delivery and cytotoxic effects of chemotherapy drugs to cells by transient permeabilization of cell membranes in a process called sonoporation. However, there is insufficient data investigating whether ultrasound and microbubbles (USMB) enhances the delivery and cytotoxicity of the nucleoside analog (NA) gemcitabine. To address this gap in the literature, cancer cells were sonicated using low frequency ultrasound in combination with Definity® microbubbles in the presence of NAs. Viability analyses show that gemcitabine in combination with USMB additively enhanced cell death, suggesting that these two therapies mediate cell death independent of one another. This was confirmed when USMB treatment did not enhance (nor impair) the retention of a radiolabeled NA molecule. Altogether, these data suggest that the laws of diffusion forcing small molecules across a barrier cannot solely describe the efficacy of sonoporation; there are obviously important biological factors specific to the molecule intended to be delivered to consider as well.