Abstract: The invention relates to a method for determining characteristic of the flow of a medium in a channel by measuring the transit times of sound waves which are transmitted between one or more transducers, and determining the characteristics from the measured transit times.In one embodiment of the method according to the invention, at least two sound waves whose transit times depend on swirl are transmitted along acoustic paths with a different sensitivity to swirl, and a measure of the swirl is determined from the measured transit times.In another embodiment, at least two sound waves whose transit times depend on the symmetry of the flow profile are transmitted along acoustic paths with a different sensitivity to symmetry, and a measure of the symmetry is determined from the measured transit times.These embodiments are preferably combined.