The results of p K a measurements on 4-substituted pyridine N-oxides show that organosilicon and organogermanium substituents are responsible for a decreased basicity relative to the tert-butyl derivative and the unsubstituted compound. No such effect is shown in the 3-substituted compounds. The results of hydrogen-bonding studies on the 4-substituted pyridine N-oxides (using methanol and phenol as acids) show that the organometallic substituents are responsible for a decreased basicity relative to the tert-butyl derivative, but not when compared to the unsubstituted compound. The effect of changing experimental conditions on the nature of the pyridine N-oxide moeity is discussed.