DNA polymerase epilson (Pol ε) is a replicative DNA polymerase with a processive 3'-5' exonuclease activity. Here we ask if Pol ε is capable of performing strand displacement synthesis, which influence many DNA processes in vivo. We found that Polε is unable to carry out extended strand displacement synthesis unless the proofreading is inactivated. However, Pol ε efficiently displaced one nucleotide when encountering double stranded DNA after filling a gap of 8 nucleotides. An abasic moiety at the 5'-end of the downstream primer was as efficiently displaced and still only with one nucleotide. Pol ε also efficiently recognized the 3'-OH innicked DNA and displaced the 5'- nucleotide, regardless if it was a normal phosphorylated deoxyribonucleotide or a ribonucleotide. A flap, mimicking a D-loop or a hairpin structure, on the 5'-end of the blocking primer inhibited Pol ε, and did not allow Pol ε to efficiently synthesize DNA up to the junction with double-stranded DNA. Finally, we show that strand displacement synthesis is limited by the processive 3'–5' exonuclease activity in Pol ε. Our results suggests that Pol ε is unable to extend D-loops during homologous recombination or participate in long-patch base excision repair based on the inhibition by the 5'–flap of the downstream primer. Our results do, however, support that Pol ε may participate in short patch base excision repair and ribonucleotide excision repair.