PurposeThis paper examines whether there are differences in the nature of the price discovery process across established versus emerging stock markets using a twenty-country sample.Design/methodology/approachThe authors analyse security returns for traces of predictability or non-randomness using variance ratio tests, Granger-Causality models and runs tests.FindingsThe findings pinpoint at predictabilities which seem inconsistent with market efficiency, and they suggest that the inherent cause of predictability differs across groups.Research limitations/implicationsThe authors present empirical evidence which may be used to attain a deeper understanding of the links between predictability and market efficiency, in view of the conflicting evidence in prior literature.Practical implicationsWhilst the pricing process in emerging markets may be hindered by delayed adjustments, in case of established markets it seems that there is a higher tendency for price reversals which could be due to prior over-reactions.Originality/valueThis study presents evidence of substantial differences in predictability across developed and emerging markets which was gleaned through the rigorous application of different empirical tests.