The DNA fragment Eco‐I (4700 kilobasepairs) from the circular chloroplast genome of Euglena gracilis is shown to be transcribed in etioplasts at all stages of light‐induced plastid development and in fully differentiated chloroplasts. Major stable transcription products are mRNAs of 14S and 17S. Using a rabbit reticulocyte lysate translation system we can show that the fragment Eco‐I selects a mRNA which directs the synthesis of a M
r 32 000–33 000 polypeptide. Eco‐I also hybridizes with a 330 basepair DNA probe cut from within the spinach chloroplast gene encoding the M
r 32 000 thylakoid membrane protein of the photosystem II reaction center. We conclude that the fragment Eco‐I carries the corresponding Euglena gracilis chloroplast gene.