In this paper we continue and extend a systematic study of plateaux in
magnetization curves of antiferromagnetic Heisenberg spin-1/2 ladders
. We first review a bosonic field-theoretical formulation of a single
XXZ chain in the presence of a magnetic field, which is then used for
an Abelian bosonization analysis of N weakly coupled chains. Predictio
ns for the universality classes of the phase transitions at the platea
ux boundaries are obtained in addition to a quantization condition for
the value of the magnetization on a plateau. These results are comple
mented by and checked against strong-coupling expansions. Finally, we
analyze the strong-coupling effective Hamiltonian for an odd number N
of cylindrically coupled chains numerically. For N = 3 we explicitly o
bserve a spin gap with a massive spinon-type fundamental excitation an
d obtain indications that this gap probably survives the limit N-->inf
inity.