Structural data, electrical transport and dielectric properties are reported for Er 2 Cu 2 O 5 . Similar to La 2 CuO 4 , this cuprate oxide reveals a two-dimensional CuO 2 network. At low temperatures and high frequencies the electrical transport is dominated by hopping conductivity processes. The dielectric constant ε 9.0(5) has been determined from high frequency measurements. At high temperatures and low frequencies d.c. conductivity contributions dominate and characterize Er 2 Cu 2 O 5 as a conventional semiconductor with a gap E G = 1.4 eV.