Methods and apparatus for the study of gastrointestinal transit in a human or animal subject. The method being for the study of a subject which has previously ingested a container containing first and second fluids that are detectable and distinguishable by MRI, which method comprises the steps of forming a first magnetic resonance image of at least a portion of the subjects GI tract in which the container is located, wherein the magnetizations of the first and second fluids are in-phase forming a second magnetic resonance image, coincident with the first image, wherein the magnetizations of the first and second fluids are out-of-phase and subtracting the second image from the first image, or vice versa, to form a composite image.
