The effect of cyclodextrins on the solubility and stability of aspalatone (acetylsalicylic acid maltol ester, AM, CAS 147249-33-0), which has been recently found to have an antithrombotic effect, was investigated. The addition of ${eta}-cyclodextrin;({eta}-CD),;dimethyl-{eta}-cyclodextrin;(DMCD);or;2-hydroxypropyl-{eta}-cyclodextrin;(HPCD)$ to the aqueous solution increased the solubility of AM concentration-dependently. From the phase solubility diagram, stability constants for $AM-{eta}-CD$, -DMCD or -HPCD complexes were calculated to be 43.1, 78.3 and $53.0;M^{-1}$. The addition of ${eta}-CD$, DMCD or HPCD to AM solution retarded the degradation rate of AM in the acidic region. However, ${eta}-CD$ and HPCD rather acted as an accelerator of degradation in the neutral and alkaline regions. DMCD had a stabilizing effect at all pHs studied.