Co-crystal data were collected from the Cambridge Structural Database , by searching for all the structures with no more than two different interacting organic molecules per asymmetric unit, using ConQuest 2021.2.0 . Hydrates, solvates, metal-organic systems, and duplicates were elimi-nated, leading to 9647 co-crystals ("positive pairs"). Nonco-crystal structures, i.e., physical mixtures of two materials that do not form a co-crystal, were sourced from literature (1274 pairs, 88%) and in-house experiments (174 pairs, 12%), resulting in 1448 "negative" molecular pairs. All molecules were represented by canonical SMILES strings and entries longer than 80 characters were removed. Salts were deleted, the stereochemistry annotations were omitted, and molecular salts were converted into neutral molecules by uncharging the components, using RDKit (v. 2023.03.3). Pairs were both molecules only contributed to one class (i.e., either exclusively partaking in "positive" pairs or in "negative" pairs) were removed. The resulting dataset contained 5240 co-crystal structures and 1392 non-co-crystal pairs, spanning different subclasses, i.e., pharmaceutical, π-π, and energetic co-crystals. Preliminary results revealed that, when including compounds that always only occurred in positive (or negative) pairs, the models learned a "shortcut", whereby any pair containing one of those molecules was always predicted as positive (or negative).