Two- and three-dimensional heteronuclear NMR experiments have been performed to identify internally bound water molecules in the solution structure of bovine heart fatty-acid-binding protein (heart FABP). NOE and rotating-frame NOE (ROE) cross peaks between protein protons and protons of bound water molecules were observed in two-dimensional H2O-ROE/NOE-1H,15N-heteronuclear single quantum coherence spectra recorded from a uniformly 13C/15N-enriched sample of bovine heart FABP. Contacts between water protons and 23 NH protons of the protein backbone were identified. The protein structure consists of 10 antiparallel β-strands (βA−βJ), forming two nearly orthogonal β-sheets, and a short helix-turn-helix motif connecting β-strands A and B. The spatial folding resembles a β-barrel. Most of the water molecules are localized in the gap between β-strands D and E, and near the two α-helices. In the delipidated heart FABP additional contacts between water molecules and NH protons could be observed using a three-dimensional rotating frame Overhauser 1H,15N heteronuclear single quantum coherence experiment obtained with a 15N-labeled sample of apo-heart FABP.