The equilibrium constant (K-f) and enthalpy (Delta(f)H) of hydrogen bond complex formation (1 : 1) between cholesterol and triacylglycerols have been determined by means of spectroscopic (IR) and calorimetric methods. The triacylglycerols used (triacetin, tributyrin, trilaurin, tripalmitin and triolein) form weak hydrogen bonds with cholesterol which are shown by the low values of K-f (from 2.4 to 3.3 M(-1)) and Delta(f)H (from -9.6 to -11.8 kJ mol(-1)). The basicity of triacylglycerols expressed by pK(HB) has a predominant effect on the enthalpy of complex formation with cholesterol.