The carotenoid composition of the following 8 species of red algae has been studied quantitatively and qualitatively : Bangia fuscopurpurea, Nemalion helminthoides, Bonnemaisonia hamifera (tetrasporophyte), Gigartina stellata, Rhodymenia palmata, Ceramium rubrum, Polysiphonia brodiaei, and Polysiphonia urceolata. Naturally occurring material of G. stellata, R. palmata, and P. brodiaei was investigated, while monoalgally cultured material was obtained from the remaining 5 species. α- and β-carotene, lutein, zeaxanthin, and small amounts of α- or β-cryptoxanthin were commonly present, but the two species P. brodiaei and P. urceolata were devoid of carotenoids containing α-ionone rings. Fucoxanthin was detected in naturally occurring material of B. fuscopurpurea, N. helminthoides, C. rubrum, and P. brodiaei, but could not be found in cultured material of the 3 first-mentioned species. The possible origin of the fucoxanthin is discussed as well as the biochemical and phylogenetic implications of the results obtained. As judged from the electronic spectrum of the total extracts, chlorophyll d was not present in any of the algae investigated. The total amounts of carotenoids and the ratio carotenoids:chlorophyll a were similar to those reported in previous work.