Aspirin (ASP) tablet containing potato starch (PS) (ASP+PS) generally took a short disintegration time. ASP tablet containing microcrystalline cellulose (MCC) (ASP+MCC) showed an optimum concentration region of MCC to give a minimum disintegration time, while (ASP+PS) did not. From the data of water intake and swelling of the powder beds of PS and MCC, PS was more affinitive to water than MCC, and from the data of capillarity, hardness and disintegration of (ASP+PS) and (ASP+MCC), it was concluded that both the mean capillary diameter and the hardness were not always correlated with the disintegration time. Taking these results into consideration, the mechanism of tablet disintegration was. discussed on the basis of cohesive and adhesive properties of particles. Finally, it might be concluded that the penetration of water into a tablet was necessary for the disintegration as the first step without being sufficient and that the work of dispersion of particles caused through the penetration of water had to overcome the binding work of particles caused through cohesion and adhesion, accordingly giving an optimum mixing ratio of drug and additive, as was shown by (ASP+MCC).