The enthalpies of combustion and vaporization of 3-buten-1-ol and 3-butyn-1-ol have been measured by static bomb combustion calorimetry and correlation gas chromatography techniques, respectively, and the gas-phase enthalpies of formation, Delta(f)H degrees(m)(g), have been determined, the values being -147.3 +/- 1.8 and 16.7 +/- 1.6 kJ mol(-1), for 3-buten-l-of and 3-butyn-l-ol, respectively. High level calculations at the G2 and G3 levels have also been carried out. Relationships between the enthalpies of formation of 1-alkanols, 1-alkenols and 1-alkynols and with the corresponding hydrocarbons have been discussed. From the calculated contributions to Delta(f)H degrees(m)(g) for the substitutions of CH3 by CH2OH, CH3CH2 by CH2=CH and CH3CH2 by CH=C, we have estimated the Delta(f)H degrees(m)(g) values for 3-buten-l-of and 3-butyn-l-ol, in excellent agreement with the experimental ones. Delta(f)H degrees(m)(g) values for I-alkenols and 1-alkynols up to 10 carbon atoms have also been estimated.