Effects of interactions between light quality and irradiance level were tested on photosynthetic pigments of the red intertidal alga Corallina elongata EUis et Soland. During a short-tern~ accommodation process (0 to 5 h), pigments adapted chromatically to light quality. R-phycoerythrin and R-phycocyanin increases were induced under green light at 180 pm01 m-2 S-' In contrast, chlorophyll a increased only under red light at the same irradiance level. In a n energy-limited situation, at a n irradiance (20 pm01 m-2 S-') close to the photosynthetic compensation point of C. elongata, the accommodation process was inhibited and no chromatic response was detected. The use of antibiotics (rifamycin and chlorarnphenicol) that inhibit chloroplastic protein synthesis revealed that red light acts on phycobiliprotein synthesis in the same way as antibiotics that suppress transcription and translation. The short-term accommodation process involves ' d e novo' synthesis of phycobiliproteins The rnechanism ot pigment accommodation is discussed in the frame of chromatic adaptation theory