The invention comprises novel polynucleotides, and related vectors, host cells, methods, and compositions, containing transcriptional enhancers providing very high levels of expression of operably-linked expressible nucleic acid sequences in eukaryotic cells. Advantageously the enhancers may be used in combination with their naturally-associated promoters and/or other genetic elements that increase transcription. The invention comprises eukaryotic expression vectors that are capable of providing increased levels of expression in many cell types over that obtainable from human or murine CMV IE enhancer/promoter elements.