  Evolutionary synthesis models have been used to study the physical properties
of unresolved populations in a wide range of scenarios. Unfortunately, their
self-consistency are difficult to test and there are some theoretical open
questions without an answer: (1) The change of the homology relations assumed
in the computation of isochrones due to the effect of stellar winds (or
rotation) and the discontinuities in the stellar evolution are not considered.
(2) There is no a consensus about how the isochrones must be integrated. (3)
The discreteness of the stellar populations (that produce an intrinsic
statistical dispersion) usually are not taken into account, and model results
are interpreted in a deterministic way instead a statistical one... The
objective of this contribution is to present some inconsistencies in the
computation and some cautions in the application of the results of such codes.
