ELMy H-modes in helium-4 plasmas provide valuable information on ELMy H-mode physics as well as a possible early low activation operational phase for next-step tokamaks, such as ITER. With this in mind a series of helium-4 H-mode experiments were performed on JET with pure helium-4 NBI auxiliary heating (up to 12MW). A set of ELMy H-mode plasmas were produced, in both the Type I ELM regime and a second regime, which showed similar characteristics to the deuterium Type III regime, but with the reverse ELM frequency dependence on power. Sawteeth were also observed, and had similar behaviour to those seen in deuterium. Compared with deuterium plasmas, Type I ELMy H-mode confinement is seen to be 28±6% poorer in helium-4 plasmas and the L-H power threshold 42±10% larger. This is the opposite of the behaviour predicted by experimental isotope mass scalings from hydrogenic plasmas. Comparison with a wider hydrogenic database, enables the effects of isotopic charge and mass to be studied independently.