  The temperature dependence of the uniform susceptibility and the ground state
energy of antiferromagnetic Heisenberg ladders with up to 6 legs has been
calculated, using the Monte Carlo loop algorithm. The susceptibilities of
even-leg-ladders show spin gaps while these of odd-leg-ladders remain finite in
the zero temperature limit. For small ratios of intra- to inter-leg couplings,
odd-leg-ladders can be mapped at low temperatures to single chains. For equal
couplings, the logarithmic corrections at low temperatures increase markedly
with the number of legs.
