Lodging of cardiovascular gas bubbles is investigated in a microfluidic model of small arteriole bifurcations. These experiments address the dynamics of the lodging mechanism of gas bubbles in bifurcations. This work is motivated by a novel gas embolotherapy technique for the potential treatment of cancer by tumor infarction. The experimental model arteriole bifurcations were constructed from a transparent elastomer (polydimethylsiloxane). A single air bubble was suspended in water within the parent tube of the bifurcation and a specified driving pressure was imposed via constant elevation reservoirs that were open to atmospheric pressure. The driving pressure and bubble size were varied, and their effects on the bubble lodging were assessed. The results show that the pressure to lodge a bubble in a bifurcation is less than to dislodge it. It was also possible to occlude an entire bifurcation and multiple bifurcation devices with bubbles. Splitting ratios were assessed in the range of lodging to dislodging pressure where we observed an instability in bubble splitting. From the results we estimate that gas bubbles from embolotherapy can lodge in vessels 21 μm or smaller in diameter. These findings may be useful in developing strategies for microbubble delivery in gas embolotherapy.