Bose-Einstein condensation of metastable helium

We have observed a Bose-Einstein condensate in a dilute gas of He-4 in the 2(3)S(1) metastable state. We find a critical temperature of (4.7 +/- 0.5) muK and a typical number of atoms at the threshold of 8 x 10(6). The maximu m number of atoms in our condensate is about 5 x 10(5). An approximate valu e for the scattering length a = (16 +/- 8 ) nm is measured. The mean elasti c collision rate at threshold is then estimated to be about 2 x 10(4) s(-1) , indicating that we are deeply in the hydrodynamic regime. The typical dec ay time of the condensate is 2 s, which places an upper bound on the rate c onstants for two-body and three-body inelastic collisions.