A larval holding chamber was designed to evaluate the movement of a new formulation of a mosquito larvicide. The chamber confines the mosquito larvae to a specific area and allows the larvicide to travel to them. After a 30-h test period, the larvicide being tested had killed all the larvae in the experimental chambers, whereas larvae confined in control chambers were not affected. The larval holding chamber is a good option for testing the movement of a larvicide through water.