Resonant Raman scattering was used as a novel, rapid, non-destructive optical technique to measure zeaxanthin levels in Flavobacterium multivorum ATCC 55238. Culture broth, after bacterial growth for 40 h, exhibited characteristic resonance Raman vibrational modes at 1159 cm(-1) (C-C stretch) and 1525 cm(-1) (C=C stretch) upon excitation at 488 nm. A striking correlation was observed between the carotenoid level as estimated by HPLC and by resonance Raman spectroscopy.