CyAL-5 is a monofunctional cyanine dye containing a free carboxylic acid group for conjugation with targeting agents containing a free amine group (e.g., drugs, proteins, peptides, and antibodies) for in vivo and in vitro imaging applications. It is water soluble, features bright fluorescence emission in the near infrared range, allows scaleup and use in multistep organic synthesis schemes, and is activated with standard reagents (e.g., HBTU, DSC) for coupling to amines.