The Alexa Fluor™ 750 SAIVI™ Antibody Labeling Kit provides a convenient means to label antibodies with an optimal degree of labeling for in vivo imaging applications (DOL; ∼2) over a 6-fold antibody concentration range with no adjustments in reaction volume, dye concentration, or antibody concentration necessary. Using this procedure, optimally labeled antibodies are ready for applications that require azide-free reagents, such as live-cell imaging or direct injection into animals.