Putative protochlorophyllide reductase cDNA clones (252 and 113) were isolated from an etiolated-oat (Avena sativa) cDNA library. These were used to indirectly characterize a further clone, p127, isolated from a A-phage gtl cDNA library. The latter (1.15 kb in length) was sequenced, and the derived amino acid sequence was shown to be remarkably similar to that derived from chemical analysis of a CNBr-cleavage fragment of the purified reductase. p127 codes for more than 95 %o of the reductase protein.