Observational tests for the Cosmological Principle are reviewed .
Assuming the FRW metric we then summarize estimates of cosmological parameters from various data sets , in particular the Cosmic Microwave Background and the 2dF galaxy redshift survey .
These and other analyses suggest a best-fit \Lambda -Cold Dark Matter model with { \Omega _ { m } } = 1 - { \Omega _ { \Lambda } } \approx 0.3 and H _ { 0 } \approx 70 km/sec/Mpc .
It is remarkable that different measurements converge to this ‘ concordance model ’ , although it remains to be seen if the two main components of this model , the dark matter and the dark energy , are real entities or just ‘ epicycles ’ .
We point out some open questions related to this fashionable model .