Metastable helium atoms were efficiently transferred from a magneto-optical
trap (MOT) to a magnetic quadrupole trap, producing samples of up to 3 x 1
0(7) magnetically trapped atoms at a temperature of about 1 mK. We observe
purely exponential decay of the samples with time constants of 9-10 s and d
erive an upper bound for the rate coefficient of inelastic Penning collisio
ns.