In a recent paper Jiang et al. (Jiang, L. J., Maret, W. and Vallee, B. L. (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 9146-9149) reported that metallothionein interacts with adenosine triphosphate (ATP) to form a 1:1 complex with a dissociation constant of K(d) = 176 ± 33 μM at pH 7.4. In an effort to characterize further this interaction using nuclear magnetic resonance spectroscopy, titration calorimetry, gel-filtration chromatography, affinity chromatography, and ultrafiltration, we were unable to find any evidence for the binding of ATP to metallothionein.