The Queen is spending a second day in hospital where she's being checked for symptoms of the stomach bug gastroenteritis.
On Sunday she was taken by car from Windsor Castle to King Edward VII Hospital in London.
She is being kept there as a precaution and apart from this bug, she is said to be in good health.
However her official engagements for this week, including a trip to Italy, will be either cancelled or postponed.
The Queen is 86 years old and this is her first hospital stay in 10 years.