The action spectra of phototaxis, photokinesis, and photophobic response of Cosmarium cucumis, C. botrytis, C. margaritiferum, and Micrasterias denticulata show peaks in the blue (about 440 nm) and red (about 670 nm) spectral regions and thus indicate the involvement of photosynthetic pigments. According to the differences in the action spectra, light-induced movement responses may be linked with photosynthesis in different ways. Results with population methods have been supported by time-lapse microcinematography.