The European Commission said consumers in the bloc have been paying up to 60% less for using their mobile phone abroad since this summer.
A study carried out by the European Regulators Group, which includes the 27 national telecom regulators, in collaboration with the European Commission has shown that the transition to the Eurotarrif by Europe's mobile phone operators is "proceeding according to plan".
By 30 August, around 200 million EU consumers had already switched to the Eurotariff, the commission said in a statement.
Many operators have moved faster than legally required and activated the Eurotariff already in July or in August, it added.
The Commission found that a number of operators throughout Europe have been offering Eurotariffs below the maximum levels allowed (49 eurocents per minute for calls made abroad and no higher than 24 eurocents for calls received abroad, excluding VAT).
Tthe lowest Eurotariffs in Europe were in The Netherlands (20 eurocents both for calls made and received), the United Kingdom (31.57 eurocents for calls made and 12.63 eurocents for calls received), Ireland (32.23 / 15.70 eurocents for calls received), Belgium (37.19 / 23.14 eurocents) and Austria (37.50 / 20.83 eurocents).
This could be a first indication of competition evolving, even though more evidence is needed to show that other operators are following this model, the commission commented.
EU Telecoms Commissioner Viviane Reding said: "I note some remaining problems regarding the transparency of some of the new roaming offers. However, after talks I had today with the ERG and with the European consumer association BEUC, I am convinced that national regulators will take this in hand as soon as possible."