Over 30 fugitives have been arrested so far
Security forces across Europe are sending tongue-in-cheek postcards to their Most Wanted criminals.
Police are using the opportunity to try and track down dangerous criminals on the run.
However, their exact addresses are unknown.
Europol say: "While most of us are enjoying a well-deserved summer break, criminals are not taking time off from crime.
"Holiday destinations have proven to be popular hiding places for criminals on the run from law enforcement.
"They might even have chosen the same destination as you".
Europol say information from the public can be vital to catch some of the fugitives.
Law enforcement across Europe - through the European Network of Fugitive Active Search Teams (ENFAST) and Europol - are asking for the public's help to find out their exact location.
The postcards feature Europe's Most Wanted fugitives, who have committed serious crimes in 21 EU countries.
They are believed to be hiding in a different country to where the crime was committed.
Since the launch of the Most Wanted campaign in early 2016, 36 Most Wanted criminals have been arrested.
Europol say at least 11 of them were apprehended as a direct result of information provided by the public.