We show that if v is a regular Laguerre-Hahn (resp.
semiclassical) linear form,then the linear form u
defined by the relation LAMBDA(x - a )u =
(x - c)v is also regular and a Laguerre-Hahn
(resp. semiclassical) linear form for every complex LAMBDA
except for a discrete set of numbers depending on v, a,
and c. We give explicitly the coefficients of the
three-term recurrence relation, the structure relation of the
orthogonal sequence associated with u, and the class of the
linear form u knowing that of v. Finally, we
apply the above results to some examples.