Void formation and vapor-liquid condensation in deionized dilute aqueous colloidal dispersions were studied for the same latex sample. The former was observed under density-matched conditions, while the latter was observed when the particles were denser than the dispersion medium. The critical concentration for void formation was found by direct observation using a confocal laser scanning microscope. Vapor-liquid condensation was observed for a dispersion of the same latex particles below the critical concentration. The critical concentrations for both phenomena were in agreement. The results clearly suggest an important role of a long-range electrostatic attractive interaction on the stability of the colloidal dispersion.