Hundreds of whales in Antarctic waters could be in danger according to environmental groups.
Japan has sent out a fleet of boats which plans to catch almost 1,000 whales over the next few months.
Hunting whales to make money has been temporarily banned but the Japanese Government claims that these whales are being caught for scientific studies.
But critics say this is an excuse and that meat from the whales caught will be sold in schools and restaurants.
The Japanese fleet set sail on Tuesday from Shimonoseki port on what they describe as a "research" programme called JARPA-2.
Over the first year they plan to catch up to 935 Mink Whales and 10 fin whales. In year two they'll start to hunt humpbacks which are extremely popular with whale watchers.
It'll be Japan's biggest whale catch in 20 years but the government claims it's for scientific purposes only and will help "monitor the Antarctic ecosystem".
Many conservation groups across the world are upset by the programme and say scientific research of whales is possible without killing them.
They describe the Japanese fleet's plans as inhumane and unnecessary and say their actions could harm fragile wildlife populations.
The environmental group Greenpeace plans to take action and is sending two boats out to the Antarctic to try to stop the killing.