The present invention provides multi-tailed lipid compounds, and salts and stereoisomers thereof, and methods of preparing the compounds. Also provided are compositions including a compound of the invention and an agent (e.g., an siRNA, mRNA, plasmid DNA, small molecule, protein, peptide). The present invention also provides methods, and kits using the compositions for delivering an agent to a subject (e.g., to the liver, spleen, or lung of the subject) or cell and for treating and / or preventing a range of diseases, such as genetic diseases, proliferative diseases, hematological diseases, neurological diseases, immunological diseases, gastrointestinal diseases (e.g., liver diseases), respiratory diseases (e.g., lung diseases), painful conditions, psychiatric disorders, metabolic disorders, and spleen diseases.