The effects of some sugars and osmotic pressure have been examined on the absorption of sulfafurazole in the rat. Statistically significant correlations were found among the hypertonic solutions between the reciprocal of osmotic pressure and AUC0--infinity or Cmax. In addition, negative correlation existed between plasma concentrations at 15 min and osmotic pressure. No significant correlations were noted among the hypotonic solutions. More attention should be paid to the osmotic pressure of formulations. The osmotic pressure of hypertonic solutions, especially, might affect absorption of drug from its dosage form.