A 55-year-old Grantham woman has been missing for over 24 hours after telling her sister she was going for a walk.
Alexandra Dryburgh left her home in Belton Grove at about midday yesterday and has not returned.
A Lincolnshire Police spokesman said: "This type of behaviour is extremely out of character for Mrs Dryburgh and police and her family are becoming increasingly concerned for her safety."
Mrs Dryburgh is described as white, around 5ft 1ins tall and medium built with hazel eyes and shoulder-length blonde/grey hair.
She was last seen wearing a green v-neck sweater and dark grey jeans with a short double-breasted black coat.
She is known to like walking in Queen Elizabeth Park, off Belton Lane.
Police are asking Mrs Dryburgh to go to her nearest police station or to call the police on 101 or 999 as soon as possible to let people know she is safe and well.
Officers are also asking anyone who sees her to get in touch with them as immediately via the 101 number.