We study the magnetic-field dependence of the cross sections for elast
ic and inelastic collisions of pairs of ultracold cesium atoms in a ma
gnetic trap, calculated with the coupled-channels method. We pay speci
al attention to atoms in the f = 3, m(f) = - 3 weak-field seeking stat
e of the lower hyperfine manifold. The cross sections show a pronounce
d resonance structure. We discuss its origin, starting from the pure b
ound singlet and triplet rovibrational Cs2 states and introducing pert
urbations due to the hyperfine and Zeeman interactions. We also discus
s the role of the centrifugal barrier in the final collision channel i
n reducing the loss of atoms from the trap due to transitions induced
by the magnetic dipole-dipole interaction.