Lacunary tungstophosphoric heteropoly compounds of Keggin structure modified with excess of manganese ions and subsequently calcined at 430-500 degreesC show high activity and selectivity in oxydehydrogenation of ethane. Steady state ethane conversion is about 25% and selectivity towards ethene 60%. The active catalytic system being a result of reaction between a lacunary heteropoly compound and excess of manganese (II) cations does not show the Keggin structure anymore.