  Four evolutionary channels leading to the formation of wide binary
millisecond pulsars are investigated. The majority of binary millisecond
pulsars are found to descend from systems in which the most massive component
undergoes a common-envelope phase prior to the supernova explosion leading to
the birth of the neutron star.
  The orbital period distribution of simulated samples of wide binary
millisecond pulsars is compared with the observed distribution of Galactic
binary millisecond pulsars for a variety of parameters describing the formation
and evolution of binaries. The distribution functions typically show a
short-period peak below 10 days and a long-period peak around 100 days. The
observed distribution is best reproduced by models with highly non-conservative
mass transfer, common-envelope efficiencies equal to or larger than unity, a
critical mass ratio for the delayed dynamical instability larger than 3, and no
or moderate supernova kicks at the birth of the neutron star. Few systems are
found with orbital periods longer than 200 days, irrespective of the accretion
efficiency of neutron stars. This occurs as a result of the upper limit on the
initial orbital periods beyond which the binary avoids the common-envelope
phase prior to the supernova explosion of the primary.
