The ribonucleic acids of green and etiolated Euglena gracilis cells show small but definite differences in their nucleotide distribution. The green organisms have a higher proportion of adenylic and uridylic acids and a lower content of cytidylic and guanylic acids. Permanently bleached cells resemble the etiolated organisms in their ribonucleic acid composition. The differences in the ribonucleic acids of the green and etiolated oragnisms are probably related to the differenced in structure and metabolism of the two types of cells. Two additional nucleotides are present in small amounts in the ribonucleic acid of Euglena gracilis. One of them is probably identical with a nucleotide recently found in the ribonucleic acids from other organisms and the second one is unknown.