A Practice Note addressing claim drafting for patent applications directed to inventions in the unpredictable technologies of chemistry and pharmaceuticals, including chemical and pharmaceutical compounds, formulations and other compositions, medical treatment methods, and chemical synthetic processes. This Note discusses planning and drafting a claim set as the key early step in patent drafting, with claims capturing the invention's key features, having the desired scope and clarity, meeting the client's commercial and competitive objectives, and satisfying statutory and formal requirements.