A new non-intrusive, Instantaneous technique to monitor the creaming/sedimentation of colloidal dispersions is reported. Here the technique is used to determine the detailed concentration profiles of water-continuous emulsions as a function of height and time. The emulsions consist of hexadecane stabilised by nonionic surfactant (Brij 35) In water In the presence and absence of a polysaccharide thickener (hydroxyethylcellulose). The technique involves the measurement of the velocity of ultrasound through the emulsion, which depends simply on the velocity through the individual phases and the bulk composition of the emulsion (provided the individual droplets are smaller than the wavelength of the ultrasound). Applications of the technique may include In-line monitoring of composition during the processing of dispersions and predictive testing of dispersion stability (shelf-life).