Studies were conducted on the relationship between dissolution rate, disintegration time, and physiological availability of seven sugar-coated multivitamin products. Dissolution rates and disintegration times were determined with the U.S.P. disintegration apparatus. A close relationship was found between in vitro disintegration time and the dissolution rate (T 50 per cent) of riboflavin for the various products. Both procedures correlated reasonably well with physiological availability as measured by urinary riboflavin excretion. It was concluded that either in vitro disintegration time or dissolution rate can provide a useful estimate of the availability to the body of riboflavin in sugar-coated tablets.