The dissolution behaviour of four commercial and two experimental formulations of frusemide tablets has been investigated using the USP rotating basket apparatus and pH 5.0 buffer at 37 degrees C as the test medium. There is a linear relationship between the percentage dissolution in 30 min and the bioavailability relative to an oral solution of frusemide over the bioavailability range 76-97%. Predicted bioavailabilities differed by no more than 2% from the measured values.