The carbon-13 spin-lattice relaxation times of the carboxyl carbons of acetic acid and its deuterated analogues (CH3COOD, CD3COOH, CD3COOD) have been measured by nuclear magnetic resonance spectroscopy. These measurements reveal that the methyl protons and the hydroxyl proton contribute roughly equally to the total dipolar relaxation of neat acetic acid. Spin-rotation relaxation is also observed in these molecules. The Ti and NOE values for the carboxyl carbon of acetic acid in aqueous solution each demonstrate a small concentration dependence in the region of high acid concentration. Although samples of 1, M acetic acid contaminated with paramagnetic metal ions show a marked pH dependence of T1 and NOE, the T1 and NOE values for purified samples are invariant with respect to pH. Some chemical implications of the above behavior are discussed.