Thermodynamic data on the hydrogen bond equilibria in octyne-donor systems are reported. CNDO/2 calculations have been carried out on hydrogen bonds formed by acetylene, HCN and fluoroform. The calculated values of dissociation energies and C—H … donor distances are in fair agreement with the experimental data. Molecular orbital calculations indicate that there is no intramolecular hydrogen bond in ortho-nitrobenzaldehyde.