Allophycocyanin, Crosslinked, Goat Anti-Rabbit IgG (H+L) is prepared from crosslinked allophycocyanin (APC) and an affinity-purified goat anti-rabbit IgG antibody, which has been adsorbed against human IgG and serum, mouse IgG and serum, and bovine serum to minimize crossreactivity. Since this phycobiliprotein is optimally excited at 633 nm, it can also be excited at 594 nm; therefore, it can be used with samples simultaneously labeled with Texas Red dye or Alexa Fluor 594 dye without the need of a second excitation source. APC can be used in flow cytometry and imaging applications and is more photostable than Cy5 conjugates.