Ab initio molecular orbital calculations at the MP 2/6-31 + G** and MP 4/6-31 + G** levels were performed to determine the preferential site of hydrogen bond formation in small molecules where more than one such site exists. For HOF, HNO, H2NF, and H2NOH the better hydrogen bond, as measured by bond strength, occurred when the proton acceptance site was the less electronegative atom. Structures and energies for all configuations were determined.