  We present nonlinear theoretical results concerning the predicted pulsation
behaviour of stellar models suitable for the sample of Cepheids belonging to
the Large Magellanic Cloud (LMC) star cluster NGC 1866. The blue and red edges
of the instability strip, transformed into the observative plane (V, B-V) by
adopting current values for the distance modulus (DM=18.57 mag., Welch et al.
1991) and for the reddening (E(B-V)=0.06 mag., Arp 1967; Walker 1974; Walker
1987), are in agreement with the observed distribution of Cepheids in the
quoted cluster. Moreover, the distribution of observational data in the Bailey
diagram (V amplitude versus period) appears in agreement with theoretical
predictions derived adopting the luminosity level predicted by canonical
evolutionary models. The role played by the direct integration of the coupling
between pulsation and convection and by the input physics on the smoothness of
light and velocity curves is briefly discussed.
