  Observations of Cepheids in the Large Magellanic Cloud, made over the last
several decades, allow us to search for evolutionary period changes. None of
the Cepheid from our sample of 378 stars stopped pulsating. Also none of them
showed a large period change which could indicate mode switching. However for
Cepheids with log P > 0.9 we found significant period changes, positive as well
as negative. A comparison between the observed period changes and theoretical
predictions shows moderate agreement with some models (Bono et al. 2000), and a
very large disagreement with others (Alibert et al. 1999). The large
differences between the models are likely caused by the very high sensitivity
of stellar evolution during core helium burning phase to even small changes in
the input physics, as discovered by Lauterborn, Refsdal and Weigert (1971).
