The effects of packaging and storage in multiple-unit and unit-dose containers on dissolution rate of model prednisone tablets are reported. USP Prednisone Dissolution Calibrator Tablets were packaged in three multiple-unit and five unit-dose containers. Packaged tablets were stored for three to six months under three conditions: 40 degrees C and 85% relative humidity (R.H.), 37 degrees C and 75% R.H., and 22 degrees C and 75% R.H. Dissolution rate was measured at pre-determined intervals during storage. For each condition tested, two separate runs of six tablets each were performed. Tablets in the least moisture-permeable containers were least affected by storage. The conditions of high heat and humidity caused the greatest change in dissolution rate. When stored at 22 degrees C and 75% R.H., little change in dissolution rate occurred in any packaged tablets. It is concluded that packaging and storage conditions affect tablet dissolution characteristics markedly. The practice of labeling repackaged tablets with the expiration date of the original container is shown to be invalid.