The main advantage of this assay is its detection sensitivity. Migration through the permeable filter can be caused by very low levels of angiogenic inducers. Prolonged studies are difficult, due to the fact that the test-agent concentration will quickly equalize between the compartment below the membrane and the compartment above the membrane. Another disadvantage is the relative difficulty in setting up the transwells. Commercially available transwells have alleviated this burden, but they are expensive.