Continuing investigations into protein-protein interactions have revealed their key role in regulating a wide range of cellular processes. Although efforts to modulate these interactions are more challenging and much less mature than work on conventional drug discovery pathways, significant progress has been made on several fronts. Highlights of recent advances involve peptide-based inhibitors, including sidechain and backbone cross-linked agents, and peptide scaffolds, as well as small-molecule inhibitors of protein-protein interactions, such as those containing terephthalate or bis-imidazole scaffolds.