A cDNA library from the protist Euglena gracilis was used to isolate and sequence an ORF coding for the elongation factor protein EF-1 alpha. The decoded amino acid sequence (MW, 48'515) is to 75-80% identical with other eukaryotic EF-1 alpha sequences but only to 24% identical with the Euglena chloroplast EF-Tu. Homologous DNA probes interact with multiple fragments of Euglena nuclear restricted DNA typical for a multimembered gene family. We present the restriction sites map of four tef nuclear gene loci and postulate that the nuclear genome also contains tef related sequences (e.g. pseudogenes). Expression of tef gene(s) is monitored by Northern hybridization and the 5' end of a stable transcript (1.5 kb) is sequenced and shown to precede the start codon by 29 positions only. The steady state concentration of the 1.5 kb mRNA is not influenced by switching cell growth conditions from dark to light (chloroplast development).